KR20200116023A - Laser device and method for transforming a laser spectrum - Google Patents

Abstract

Provided are a laser device and a method of transforming laser spectrum, which provide a laser frequency stabilization and significant narrowing a laser spectrum. A laser device comprises: at least one multiple longitudinal mode laser (L) for generating a laser light having a spectrum of multiple longitudinal modes; at least one high quality factor (high-Q) microresonator (M) optically feedback coupled to the at least one multiple longitudinal mode laser (L); and a tuner (TU) for tuning the spectrum of multiple longitudinal modes of the laser light. The laser device is configured to output an output laser light having an output spectrum with at least one dominant longitudinal laser mode each at a reduced linewidth of the dominant longitudinal laser mode. The laser device allows increasing an emission power of a narrow linewidth lasing without an additional amplification while keeping a compact size of a device with a limited number of optical elements.

Description

Laser device and method for transforming a laser spectrum

It relates to a laser device and a laser spectrum conversion method.

There are various approaches to laser frequency stabilization and laser spectrum reduction. Certain sources of information set forth below may be helpful in understanding the physical principles and/or specific materials and technical means on which the present disclosure is based.

A common approach to passive laser frequency stabilization and laser spectrum reduction is to use resonant optical feedback from external optical elements. Various perturbations such as temperature changes and vibrations cause the laser to fluctuate in wavelength, power level and light phase. More stable external optical elements that provide spectrally selective optical feedback, such as diffraction gratings, high finesse (high-Q) Fabry-Perot (FP) cavities, or a combination thereof, enable narrowing the laser spectrum and stable frequencies of laser generation. . When using high-Q (high quality factor) cavities, the stabilized laser is well above the threshold and optimal frequency stabilization is achieved with weak optical feedback (<10 ^-4 ). The external high-Q cavity optical feedback technology uses a diffraction grating to provide higher output power and better short-term stability than stabilization. However, the high-finesse FP cavity, which is successfully used in many laser stabilization applications, is relatively large and is only used in the laboratory. In addition, high-finesse mirror coatings are well suited for a narrow range of wavelengths.

Other important prototypes are dual wavelength lasers required for spectroscopy, LIDAR applications, holographic interferometers, optical terahertz sources and other applications. First of all, a broadly separated (hundreds of nm) dual wavelength device could be realized using, for example, dual wavelength lasing for two different ions in a single solid-state laser material or simultaneous lasing for two wavelengths in a single ion. I can. Traditionally, two-frequency generation with small wavelength differences (up to several tens of nm) has been realized using electro-optical or acousto-optic modulation of single-frequency laser radiation. However, these devices are not very compact. To date, various technologies have been developed to achieve dual wavelength operation in small diode laser systems, which can be mainly classified into (1) monolithic dual wavelength diode lasers and (2) diode laser systems based on other external cavity feedback technologies. Monolithic double-wavelength diode lasers show stable double-wavelength operation, but the tuning range of the frequency difference between the two wavelengths is limited, and the output power is usually less than 500mW. Bulk diffraction gratings for double-Littman and double-Littrow external cavity technologies, dual fiber Bragg gratings, dual period hologram elements and other frequency choices such as single wavelength volume Bragg gratings or monolithic multiplexing Bragg gratings Elements have been used in external cavity feedback technology. Since the gain medium of external cavity dual wavelength diode laser systems is usually a single mode ridge waveguide diode laser, the output power of these laser systems is typically hundreds of milliwatts.

A laser device and a laser spectrum conversion method that significantly narrows the laser spectrum and stabilizes the laser frequency due to efficient conversion of its power from a spectrum containing a plurality of relatively wide longitudinal modes to a narrow single mode or a spectrum having a plurality of narrow spectral modes. to provide.

The proposed invention will now be described by way of example and is not limited with reference to the description and drawings provided below.

This summary is presented prior to the detailed description of certain exemplary embodiments to provide an overview of aspects of the claimed invention that are further described below, and is not intended to define or limit the scope of the invention in any way.

The present disclosure provides multiple longitudinal locked to high-Q micro resonators to deliver one or multiple powerful narrow laser lines with optical frequency combs typically generated with optical frequency combs, typically less than about 1 kHz linewidth, in some cases one or multiple parameters. It is to provide a compact device based on a mode laser.

The technical result of the present disclosure consists in increasing the emission power of narrow line width lasing without additional amplification while maintaining the compact size of the device with a limited number of optical elements. The increased emission power is the result of the use of a broad spectrum multi-longitudinal mode laser that is much more powerful than a conventional DFB laser locked to a WGM microresonator for spectral narrowing and generating optical frequency comb teeth. In this case, the longitudinal mode competition under the condition of resonant optical feedback leads to effective laser power redistribution which is advantageous for one or more narrow laser lines at the resonant frequency of the high-Q microresonator. Further, the present disclosure provides a more compact and powerful dual wavelength or multi-wavelength laser device that produces a narrow linewidth and has at least one high-Q external cavity. Further, the present disclosure provides a compact, powerful source of optical frequency combs generated with one or multiple parameters by using at least one high-Q micro resonator.

A laser device according to one type comprises one or more multiple longitudinal mode lasers for generating laser light having multiple longitudinal mode spectra; One or more high-quality coefficient (high-Q) micro resonators optically feedback-coupled to the one or more multiple longitudinal mode lasers; At least one multiple longitudinal mode with each resonant frequency of the at least one high-Q micro-resonator to obtain at least one matching frequency multiple longitudinal modes of the laser light to match each of the at least one frequency of each individual longitudinal mode of the laser An output laser light having an output spectrum having at least one of the at least one matching frequency and at least one dominant longitudinal laser mode each at a reduced linewidth of the predominant longitudinal laser mode. It may be provided to couple.

One or more high-Q micro-resonators are made of a material having an intensity dependent refractive index, and the laser device may be arranged to generate one or more optical frequency combs, wherein each one or more optical frequency combs are at least one dominant longitudinal If the laser mode has a power greater than the pump threshold of optical frequency comb generation, it can be parametrically generated by one of the at least one dominant longitudinal laser mode.

The tuning unit may be arranged to change the spacing of the longitudinal modes in the frequency domain and to change the frequency of each of the individual longitudinal modes of the at least one multiple longitudinal mode laser.

The at least one high-Q micro-resonator may be arranged to provide optical feedback to the at least one multiple longitudinal mode laser by each generating at least one reverse propagation mode at one of the at least one matching frequency.

The at least one multiple longitudinal mode laser may be a power semiconductor laser diode.

One or more multiple longitudinal mode lasers and one or more high-Q micro-resonators can be fabricated on the same chip using microlithography.

The tuning unit is arranged to control the injection current of the at least one multiple longitudinal mode laser and/or each of the at least one multiple longitudinal mode laser, or the temperature of each laser active medium individually at least one multiple longitudinal mode laser. I can.

The at least one multiple longitudinal mode laser can be optically feedback coupled to the at least one high-Q micro resonator by recoupling the light scattered from the at least one high-Q micro resonator back to the at least one multiple longitudinal mode laser. have.

One or more of the at least one multiple longitudinal mode laser may be optically feedback coupled to one or more of the at least one high-Q micro resonator via a coupling element.

The coupling element may include at least one of a total internal reflection prism, a tapered optical fiber, and a waveguide.

One or more of the at least one high-Q micro resonator may be provided with an additional coupling element.

The additional coupling element combines one or many of the multiple dominant longitudinal laser modes generated in one or multiple of the at least one high-Q microresonator, or of the dominant longitudinal laser modes to filter out the non-resonant portion of the output spectrum. It may be provided to combine one or a plurality of optical frequency combs generated in one or a plurality of at least one high-Q micro resonator.

The at least one optical frequency comb may be a dissipative Kerr soliton optical comb.

The tuning unit may be further provided to tune the resonant frequencies of the high-Q modes of the at least one high-Q micro resonator by changing the interval of the high-Q mode in the frequency domain and changing the resonant frequency of each of the high-Q modes. .

The tuning unit may be further provided to control the temperature of the at least one high-Q micro resonator, and/or the external pressure applied to each of the at least one high-Q micro resonator or individually at least one high-Q micro resonator. have.

At least one high-Q micro-resonator is made of an electro-optical material whose refractive index changes in response to an electromagnetic field applied to the at least one high-Q micro-resonator, and the tuning unit comprises at least one high-Q micro-resonator or at least one high -Q It can be provided to control the electromagnetic field individually applied to each of the micro-resonators.

At least one high-Q micro resonator may be a WGM micro resonator.

A method of converting a laser spectrum according to one type comprises: generating laser light having a spectrum of multiple longitudinal modes by means of at least one multiple longitudinal mode laser; With each resonant frequency of at least one high-Q micro-resonator optically feedback coupled to at least one multi-longitudinal mode laser to obtain at least one matched frequency, the spectrum of the multiple longitudinal modes of the laser light is at least Tuning to match each of at least one frequency of a respective longitudinal mode of one multiple longitudinal mode laser; And coupling output laser light having an output spectrum to at least one dominant longitudinal laser mode each at one of the at least one matched frequency and at a reduced linewidth of the dominant longitudinal laser mode.

At least one high-Q microresonator is made of a material having an intensity dependent refractive index, and the method comprises at least one of the at least one dominant longitudinal laser mode having a power exceeding the pump threshold of optical frequency comb generation. It may further comprise generating at least one optical frequency comb in a parametric manner by each of the dominant longitudinal laser modes.

The spectrum of the multiple longitudinal modes can be tuned by varying the spacing of the longitudinal modes in the frequency domain, and by changing the frequency of each of the individual longitudinal modes of the at least one multiple longitudinal mode laser.

The at least one high-Q micro resonator may be arranged to provide optical feedback to the at least one multi-longitudinal mode laser by each generating at least one reverse propagation mode at one of the at least one matching frequency.

The spectrum of the longitudinal mode is tuned by controlling the injection current of the at least one multiple longitudinal mode laser and/or the temperature of the laser active medium of each of the at least one multiple longitudinal mode laser or individually at least one multiple longitudinal mode laser. Can be.

At least one reverse propagation mode coupled back to the at least one multi-longitudinal mode laser may be generated due to resonant Rayleigh scattering in at least one high-Q micro resonator.

One or more of the at least one multiple longitudinal mode laser may be optically feedback coupled to one or more of the at least one high-Q micro resonator via a coupling element.

The coupling element may include at least one of a total internal reflection prism, a tapered optical fiber, and a waveguide.

One or more of the at least one high-Q micro resonator may be provided with an additional coupling element.

One or more dominant longitudinal laser modes or one or more dominant longitudinal laser modes and at least one high-Q micro via an additional coupling element such that one or more optical frequency combs filter the non-resonant portion of the output spectrum. It may be coupled from one or more of the resonators.

The resonant frequency of the high-Q mode of at least one high-Q micro resonator can be tuned by changing the interval of the high-Q mode in the frequency domain and changing the resonant frequency of each of the high-Q modes.

The method may further include controlling a temperature of the at least one high-Q micro resonator and/or an external pressure applied to each of the at least one high-Q micro resonator or individually at least one high-Q micro resonator.

The at least one high-Q micro resonator is made of an electro-optical material whose refractive index changes in response to an electromagnetic field applied to the at least one high-Q micro resonator, the method comprising at least one high-Q micro resonator, preferably Alternatively, individually controlling the electromagnetic field applied to each of the at least one or more high-Q micro resonators may be further included.

At least one high-Q micro resonator may be a WGM micro resonator.

According to one type, a method of operating a laser device having the above characteristics includes at least one spectrum of multiple longitudinal modes of laser light at each resonance frequency of at least one high-Q micro-resonator to obtain at least one matched frequency. Tuning to match each of the at least one frequency of the respective longitudinal mode of the multiple longitudinal mode lasers of the; And coupling an output laser light having an output spectrum in at least one dominant longitudinal laser mode each to one of the at least one matching frequency and a reduced linewidth of the dominant longitudinal laser mode.

According to the laser apparatus and laser spectrum conversion method according to the embodiment, laser frequency stabilization due to efficient conversion of its power from a spectrum including a plurality of relatively wide longitudinal modes into a narrow single mode or into a spectrum having a plurality of narrow spectral modes And can significantly narrow the laser spectrum. .

The described effect can occur by two mechanisms. The first is the resonant light feedback of the high-Q optical microresonator as a result of re-injecting the laser light scattered from the high-quality factor (high-Q) microresonator into the laser. And the second is laser longitudinal mode competition in optical feedback conditions leading to an efficient redistribution of laser power, which is advantageous for one or many narrow laser lines.

In the case of a microresonator made of a material with an intensity-dependent refractive index, the generation of a spectrally narrow laser line at a power level higher than the pump threshold is parametrically generated with a plurality of narrow spectral modes spaced apart by a fixed frequency value. One or multiple optical frequency combs may be provided.

Moreover, it provides a compact high-coherent powerful light source, a light frequency comb source or a small multi-wavelength laser device that provides simultaneous stable generation at multiple wavelengths (frequency), which is very important for many practical applications. It is possible to provide a laser device that can be applied to measurement using a heterodyne effect, a small spectroscopic sensor including a wearable device, a coherent LIDAR, and optical data transmission.

Reference will now be made to exemplary embodiments, which are presented in the detailed description below and are intended to be read in conjunction with the accompanying drawings. The accompanying drawings are not intended to define or limit the scope in any way, but to provide specific examples of their implementation. Those skilled in the art will understand that other embodiments, modifications, or equivalent substitutions may become apparent based on the teachings of this description, and that all such embodiments, modifications, and equivalent substitutions are considered to be included.
The drawings are provided for illustrative purposes only to aid in reading and understanding the description, and should not be regarded as limiting or limiting the scope.
1A shows one multiple longitudinal mode laser coupled to one crystalline optical high-Q micro resonator (M) enabling propagation of high-Q mode using a coupling element as a total internal reflection prism (C) ( L) is shown.
1b shows one multiple longitudinal mode laser (L) coupled to one optical high-Q micro resonator (M) using a coupling element (C). An additional coupling element C2 can be used to filter out non-resonant portions of the generated laser light.
2 shows a plurality of coupling elements C ₁ . Multiple parallel high-Q micro resonators M ₁ through C _N … An example of one multiple longitudinal mode laser L ₁ simultaneously locked to M _N is shown schematically.
Figure 3 shows another when one multiple longitudinal mode laser (L1) is simultaneously locked to multiple series high-Q micro-resonators (M ₁ … M _N ) through multiple coupling elements (C ₁ … C _N ). An example is schematically shown.
4 schematically illustrates another example when a plurality of multiple longitudinal mode lasers (L ₁ … L _m ) are simultaneously locked to one high-Q micro resonator (M ₁ ).
Figure 5 shows a plurality of parallel and series NP high-Q micro-resonators M _PN with a plurality of multiple longitudinal mode lasers L ₁ . An example of how L _m is locked at the same time is shown.
6A shows an embodiment of a tuning unit configuration.
6B shows an example of a measurement equipment scheme used to control spectrum transformation.
Figure 7 shows the oscillogram (solid curve) of the signal of the photodetector (D) of Figure 1 and the power of the resonant Rayleigh backscattering (dotted curve) while the frequency of the multiple longitudinal mode laser (L) is swept along the horizontal axis. .
8 shows an example of converting the spectrum of multiple longitudinal modes of a longitudinal mode laser into an output spectrum of the output laser light generated by the laser device, and one frequency of the individual longitudinal mode is one of the high-Q microresonators. It is shown that the spectrum has one dominant longitudinal laser mode when matched with the resonant frequency of.
9A is a diagram of at least one multiple longitudinal mode laser locked to at least one high-Q micro resonator when one frequency of the individual longitudinal mode matches one resonant frequency of at least one high-Q micro resonator. The result of converting the spectrum is shown.
Figure 9b shows at least one multiple longitudinal mode laser locked to at least one high-Q micro-resonator when the two frequencies of the respective longitudinal modes coincide with the two resonant frequencies of at least one high-Q micro-resonator. The result of converting the spectrum is shown.
Figure 9c shows at least one multiple longitudinal mode laser locked to at least one high-Q micro-resonator when the four frequencies of the individual longitudinal modes coincide with the four resonant frequencies of at least one high-Q microresonator. The result of converting the spectrum is shown.
10A shows the result of transforming the spectrum of a multiple longitudinal mode laser locked to a magnesium fluoride high-Q microresonator with the generation of one dominant longitudinal laser mode.
10B shows an example of an optical spectrum of an optical frequency comb generated in a parametric manner in the case of FIG. 9A.
11A shows two lights simultaneously generated when a multi-longitudinal mode laser diode is locked to a magnesium fluoride high-Q microresonator with the generation of two dominant longitudinal laser modes pumping a frequency comb generated in a parametric manner. The optical spectrum of the frequency comb (the curve at the center of Fig. 11A and the curve at the other part) is shown.
11B shows the radio frequency spectrum beating the narrow mode of the comb.
FIG. 12A schematically shows a top view of a laser device having at least one multiple longitudinal mode laser and at least one high-Q micro resonator fabricated on the same chip using microlithography.
Fig. 12b schematically shows a side view of the laser device of Fig. 12a.

Hereinafter, exemplary embodiments will be described in detail with reference to the accompanying drawings. In the following drawings, the same reference numerals refer to the same elements, and the size of each element in the drawings may be exaggerated for clarity and convenience of description. The embodiments described below are merely exemplary, and various modifications may be made from these embodiments.

One approach to laser frequency stabilization and spectrum reduction is the implementation of a compact, high-Q crystalline WGM microresonator. The compact ring resonator has a characteristic dimension of 0.1-10 mm and can have ultra-high quality coefficients from the ultraviolet (UV) region to the mid-infrared (MIR) region. The optical feedback of the high-Q crystalline WGM microresonator is based on resonant Rayleigh scattering because of the surface non-uniformity of the resonator: when the laser light frequency matches the frequency of the resonator mode, some light is reflected back to the laser. In other words, the spectrally selected portion of the laser light that is self-scanned on the laser fixes the generation frequency. This process, called "self-injection locking", provides fast optical feedback, which greatly narrows the laser spectrum. Today, linewidth reduction and frequency stabilization of various types of lasers, including quantum cascade lasers and distributed feedback (DFB) lasers, have been reported due to self-injection locking on WGM microresonators, and in fact, linewidth reduction down to ~Hz levels has been demonstrated.

Self-injection locking using WGM micro-resonators is applied to the frequency stabilization and spectrum reduction of pre-stabilized single-mode laser diodes, mainly by placing the grating on a laser active medium such as a DFB laser or by implementing some type of Bragg reflector. . The main reason is that the laser frequency stability is improved when only one micro-resonator mode is within the laser gain bandwidth, since unwanted multi-mode lasing and mode contention can occur when multiple modes produce the same optical feedback. Usually, the ultrahigh-Q WGM microresonator has a high spectral density in the resonant mode, and the above-mentioned laser with preliminary stabilization has a relatively narrow line width ~ 1-10 MHz and an emission power of about tens of milliwatts. A crystalline MgF2 optical microresonator pumped with a small dispersion feedback (DFB) laser that is self-injection locked into an optical resonator is known to provide a small optical frequency comb source. When the DFB laser is coupled to an optical microresonator using a total internal reflection prism, part of the light is scattered back into the DFB laser due to resonant Rayleigh scattering, resulting in self-injection locking with the laser frequency to the frequency of the selected optical microresonator mode. This self-injection locking effect narrows the laser line width by 3-4 when compared to the line width of a free-running DFB laser required to efficiently combine light from the laser to the optical micro-resonator and generate an optical frequency comb. However, the more powerful, narrow line-width lasers required for many applications, including coherent LIDAR and spectroscopy, require subsequent amplification, resulting in loss of miniaturization. Also, DFB lasers cannot be used at all desired wavelengths corresponding to specific atomic light transitions. A semiconductor optical amplifier (SOA), available in a wider wavelength range, is used for stabilization of micro-resonators, where the pre-generated spectrum is narrowed using a diffraction grating cavity. The two cavity configuration usually leads to complex devices that cannot be compact.

According to the laser device according to the embodiment, the laser frequency stabilization and the laser spectrum are significantly reduced due to the efficient conversion of its power from a spectrum comprising a plurality of relatively wide longitudinal modes into a narrow single mode or into a spectrum having a plurality of narrow spectral modes. Since it can be narrowed, subsequent amplification or two-cavity configuration is unnecessary, and a compact laser device can be implemented.

In particular, the embodiment comprises at least one multiple longitudinal mode laser, high-Q mode propagation and optical feedback coupled to at least one multiple longitudinal mode laser for generating laser light having a spectrum of multiple longitudinal modes. At least one optical high-Q micro-resonator, each resonant frequency of at least one high-Q micro-resonator to obtain at least one matched frequency, at least one multiple longitudinal mode of at least one of the individual modes of the laser It provides a laser apparatus comprising a tuning unit that tunes the spectrum of multiple longitudinal modes of laser light to match each of the frequencies. The laser device is configured to generate an output laser light having a converted spectrum each having at least one dominant longitudinal laser mode at one of the at least one matching frequency and at a reduced linewidth of the dominant longitudinal mode. In addition, the embodiments provide a method of operating a laser device.

The various illustrative embodiments should in no case be construed as defining or limiting the scope of the claims, but will be understood to be other materials and technical means equivalent or apparent to those listed. Hereinafter, it may be expected by a person skilled in the art to perform various operations, functions, method steps, and the like as described herein. This detailed description is not intended to define or limit the scope of the claims, and should be defined only by reference to the appended claims.

The term "high-Q microresonator" as used in this disclosure defines a light-confining and characteristic dimension of about 0.01-10 mm, often a traveling wave microcavity for localization of a light field of approximately micrometer-scale size in approximately one direction. it means. The light is internally reflected off the edge of the high-Q microresonator in a manner similar to a series of standing-wave light high-Q modes or loops that create high-Q resonances similar to what may be present in a vibrating guitar string. In the high-Q micro resonator, the quality factor Q of the high-Q mode exceeds 10 ⁵ , and may be, for example, about 10 ⁶ -10 ⁹ , for example 10 ⁸ -10 ^{9 or} more. For example, a high-Q microresonator can be a spherical, toroidal, disk, or any other type of high-Q Whispering-Gallery Mode (WGM) microresonator with a closed optical path within the cavity of the resonator. , This enables propagation of the whispering-gallery mode, which is a kind of light wave that can move around the concave surface. It was first discovered about sound waves at the Whispering Gallery in St. Paul's Cathedral in London, and may also exist in light and other waves. In another particular case, the high-Q micro-resonator may be an integrated resonator of different configurations with closed optical paths along the waveguides that enable propagation of high-Q specific waveguide modes. Alternatively, the high-Q microresonator could be a linear Fabry-Perot-like resonator with a closed optical path length equal to the product of the multiplied longitudinal resonator length and the refractive index of the resonator material. In this specification, the terms “high quality factor micro resonator” and “high-Q micro resonator” are given the same meaning and may be used interchangeably depending on the context. The terms "high quality factor mode" and "high-Q mode" are provided with the same meaning for the high-Q mode propagating in the high-Q micro resonator, and may be used interchangeably depending on the situation.

According to an embodiment, it consists in increasing the emission power of a narrow line width lasing without further amplification, which provides a compact size of the device with a limited number of optical elements. The increase in power may be the result of using a semiconductor broadband multiple longitudinal mode laser that is much more powerful than a semiconductor distributed feedback (DFB) laser locked to a WGM microresonator. Single-mode DFB lasers with a characteristic spectral width of 1-10 MHz coupled to magnesium fluoride WGMs microresonators are narrow (<1 kHz due to the resonant optical feedback provided by Rayleigh scattering in the microresonators coupled back to the DFB laser). ) It is known to provide linewidth laser generation. Also, a small optical frequency comb source is well known when a crystalline MgF2 optical WGM microresonator is pumped with a small distributed feedback (DFB) laser that is self-injecting into the optical resonator. When the DFB laser is coupled to an optical WGM microresonator using a total internal reflection prism, part of the light is scattered back to the DFB laser due to resonant Rayleigh scattering, which induces self-injection locking to the frequency of the selected optical WGM microresonator mode. have. This self-injection locking effect efficiently couples light from the laser to the optical WGM microresonator, and can narrow the laser line width by 3-4 compared to the line width of a free-running DFB laser (1-10 MHz) required to generate an optical frequency comb. .

Available DFB lasers have a limited emission power, for example about 50 mW, and a limited operating spectral range. In some embodiments, a more powerful multiple longitudinal mode laser, also known as a Fabry-Perot laser coupled with a high-Q microresonator, similarly provides narrow linewidth generation, but the power can be increased. High power narrow line width generation can provide high power optical frequency combs generated in a parametric manner. A multiple longitudinal mode laser may include a Fabry-Parot resonator, usually having two planar-parallel mirrors or two concave mirrors, and an active medium enclosed inside the resonator. The output spectrum of the laser has a width defined by the gain band of the laser active medium filled with spectral lines spaced by a fixed frequency that is inversely proportional to the length of the Fabry-Perot resonator. The line width of the spectral line depends on the reflectance of the mirrors of the Fabry-Perot resonator. In this description, the terms "multi-longitudinal mode" or "laser spectral line" are given the same meaning and may be used interchangeably depending on the context. In the context of this application, the term “laser spectral line” may be a separate longitudinal mode lasing line.

The initial mode preselection and pre-stabilization of the laser diode is not required to obtain a stable narrow linewidth, single frequency lasing, and a high-Q microresonator can handle all these applications efficiently. As a result, simpler and cheaper Fabry-Pιrot (FP) laser diodes with higher power can be used. For example, the spectrum of a typical near-infrared semiconductor edge emitting laser has 20-40 MHz wide spectral lines separated by a frequency of 15-40 GHz over a wide spectral range of 10-20 nm. In one type of embodiment, if such a laser is coupled to the high-Q micro resonator and the frequency of one of the individual longitudinal modes of the laser matches one of the resonant frequencies of the high-Q micro resonator, then from the high-Q micro resonator The resonant optical feedback of occurs at the matched frequency. Next, the longitudinal mode competition under the resonant optical feedback condition leads to an effective laser power redistribution which favors one dominant longitudinal laser mode at the matched frequency and reduces the line width to the resonant mode line width of the micro resonator. The terms "predominant longitudinal laser mode" and "spectral narrow laser line" as used herein are given the same meaning and may be used interchangeably depending on the situation. In the context of the present application, the term "spectral narrow laser line" refers to the dominant longitudinal laser mode lasing line, whose line width can be reduced to the resonance mode line width of the micro resonator by interaction with the high-Q micro resonator. .

In the context of the present disclosure, the terms “matching” and “matched frequency” may mean the following. Usually, the individual longitudinal mode linewidth (20-40MHz) is much wider than the resonant mode linewidth (100kHz-1MHz) of a microresonator. Considering this, when tuning the laser spectrum, it is necessary to obtain a region where the spectral curve of the individual longitudinal mode and the spectral curve of the resonant mode of the micro resonator overlap in the frequency domain. On the other hand, some of the laser power of the individual longitudinal modes corresponding to the overlapping area will be sufficient to provide optical feedback from the micro resonator. In this case, the matching frequency corresponds to the resonant frequency of the microresonator, and the center of the spectral curve of the individual longitudinal mode and the center of the spectral curve of the resonant mode of the microresonator may not coincide in the frequency domain and may only be close to each other. . Usually “matching” can be achieved if the resonant frequency of the microresonator is on the slope of the spectral curve of the individual longitudinal mode. Obviously, the different relative positions of the spectral curve of the individual longitudinal mode and the spectral curve of the resonant mode of the micro resonator can be matched, corresponding to providing different optical feedback powers from the micro resonator. The feedback power level of multiple simultaneously locked individual longitudinal modes can significantly affect the competition and redistribution of laser power in favor of one or more dominant longitudinal laser modes. The dominant longitudinal laser mode corresponds to the longitudinal laser mode at a matched frequency, where the power amplitude may exceed the amplitude of the nearest neighbor mode or side mode several times as a result of mode competition. In addition, the side mode can be suppressed as a result of redistribution of the laser power in favor of the dominant longitudinal mode. The Side Mode Suppression Ratio (SMSR) parameter, which is the ratio of the dominant mode amplitude to the amplitude of the nearest side mode, is characterized by the amount of normal mode dominance. In general, in the case of the locking mode according to the present application, the SMSR may be in the range of about 30-60dB, for example, in the range of about 40-60dB. For example, about 40dB can often provide a sufficient amount of mode advantage for the purpose of this application.

According to an embodiment, since a normal multi-longitudinal mode laser is much more powerful than a DFB laser (up to 500 mW in continuous wave), the resulting power of narrow line width generation is increased and the power of the generated optical frequency comb can potentially be increased. . Semiconductor Fabry-Perot lasers cover a wider spectral range than DFB lasers, so narrow linewidth generation can be achieved using coupling with high-Q micro-resonators at any optical frequency required for a specific application.

When multiple longitudinal mode lasers are locked to high-Q micro resonators, when multiple frequencies of multiple longitudinal modes of multiple longitudinal mode lasers coincide with multiple resonant frequencies of high-Q micro resonators at the same time, multiple It can be configured as an option to simultaneously deliver the dominant longitudinal laser modes. It provides the compact size of the device with only one multi-longitudinal mode laser and one high-Q micro-resonator acting as an external cavity, especially the most compact and powerful dual-wavelength or even multi-wavelength laser devices with a stable frequency and reduced. Makes it possible.

In one embodiment shown in Figure 1A, the multi-longitudinal mode laser (L) is optically feedback-coupled to the high-Q crystalline optical microresonator (M) through a coupling element (C), such as a total internal reflection coupling prism. do. The high-Q micro-resonator (M) may be a high-Q WGMs micro-resonator that enables propagation of cyclic whispering gallery modes (WGMs). The laser device has a tuning unit TU for tuning the spectrum of multiple longitudinal modes of the laser light 1 produced by the multiple longitudinal mode laser L. The tuning unit (TU) varies the spacing of the longitudinal modes in the frequency domain so as to obtain at least one matched frequency, each of at least one frequency of the respective longitudinal mode of the longitudinal mode laser (L) being high- Q may be configured to change the frequency of each of the individual longitudinal modes of the laser L to match each resonant frequency in the frequency domain of the micro resonator M. For example, if "at least one" used in the phrase "each of at least one frequency of the individual longitudinal mode" is equal to one, then one of one individual longitudinal mode of the multiple longitudinal mode laser (L) Each of the frequencies of can be matched to the respective resonant frequency of one of the high-Q micro resonators. In this case, one matched frequency can be obtained for one frequency pair. If "at least one" used in the phrase "each of the at least one frequency of the individual longitudinal mode" is equal to 3, this means that each of the 3 frequencies of the 3 separate longitudinal modes of the multiple longitudinal mode laser (L) This means that the high-Q micro resonator is matched to each resonant frequency. In this case, three matched frequencies are obtained for three frequency pairs, where the first frequency of the first individual longitudinal mode is matched with the first resonant frequency, and the second frequency of the second individual longitudinal mode is the second The resonant frequency is matched, and the third frequency of the third individual longitudinal mode may be matched with the third resonant frequency. If "at least one" used in the phrase "each of at least one frequency of the individual longitudinal mode" is equal to N, it means that N frequencies of the N individual longitudinal modes of the multiple longitudinal mode laser (L) It means that it matches each of the N resonance frequencies of the high-Q micro resonator, where N is a number greater than or equal to 1. In this case, N matching frequencies are obtained for N frequency pairs, where the first frequency of the first individual longitudinal mode is matched with the first resonant frequency, and the second frequency of the second individual longitudinal mode is the second Is matched with the resonant frequency,... , The Nth frequency of the Nth individual longitudinal mode is matched with the Nth resonance frequency.

The high-Q micro-resonator (M) is directed to at least one multi-longitudinal mode laser (L) by generating at least one reverse propagation mode each at one of the at least one matching frequency (see “mode-s” in Fig. 1A). Can provide optical feedback. In some embodiments, when the high-Q micro resonator M is a high-Q WGM micro resonator, the high-Q micro resonator M is each at least one reverse propagation mode whispering at one of the at least one matching frequency. By creating gallery modes (WGMs) it is possible to provide optical feedback to at least one multiple longitudinal mode laser (L). At least one back propagation mode (mode-s) can be coupled back to the multiple longitudinal mode laser (L). The laser light (2) entering the photodetector (D) is coupled from the high-Q micro-resonator (M) through the total internal reflection coupling prism (C) and is not coupled to the high-Q micro-resonator (M). The laser light 1 is integrated. At least one reverse propagation mode (mode-s) coupled back to the multiple longitudinal mode laser (L) in the form of a light wave (S) is provided by resonant Rayleigh scattering to the high-Q microresonator. Under the condition of resonant optical feedback, the power of the multiple longitudinal mode lasers L can be effectively redistributed due to longitudinal mode competition in favor of each at least one dominant longitudinal laser mode at one of the at least one matching frequency. The laser device is configured to generate an output laser light having an output spectrum having at least one dominant longitudinal laser mode at a reduced linewidth of at least one dominant longitudinal mode (compared to each individual longitudinal mode of the laser). I can. For example, if 5 matching frequencies are obtained, then 5 dominant longitudinal laser modes will be present in the output spectrum. Meanwhile, as schematically shown in Fig. 1A, instead of the total internal reflection prism, another type of coupling element ⓒ such as a tapered optical fiber or a waveguide may be used. The modification of a tapered optical fiber or waveguide connected to one side with one or more multiple longitudinal mode lasers also makes it possible to couple simultaneously with one or more micro resonators. For example, a tapered optical fiber can be coupled simultaneously by two toroidal microresonators and their bottleneck parts from opposite sides of each other. Waveguides arranged with micro-resonators on the same semiconductor chip can be simultaneously coupled to three or more micro-resonators located at a sub-wavelength distance from them.

Figure 2 is a plurality of coupling elements (C ₁ ... C _N) a plurality of parallel high-Q micro-resonator through (M ₁ ... M _N), for example, WGM one multi-species the locking at the same time the micro resonator direction mode laser ( An example of L ₁ ) is schematically shown. The laser light 1 with the spectrum of multiple longitudinal modes is branched so that each high-Q micro resonator receives the laser light 1. The tuning unit (TU) (not shown) is the individual longitudinal direction of the longitudinal mode laser (L ₁ ) with the resonant frequencies of multiple high-Q micro resonators (M ₁ … M _N ) to obtain at least one matching frequency. The spectrum of multiple longitudinal modes of laser light 1 is tuned to match each of the at least one frequency of the mode. For example, four matching frequencies can be obtained for one laser (L ₁ ) and three high-Q micro resonators (M ₁ , M ₂ , M ₃ ), where laser (L ₁ ) and high- The first matching frequency can be obtained for the Q micro resonator (M ₁ ), and the second and third matching frequencies can be obtained for the laser (L ₁ ) and the high-Q micro resonator (M ₂ ), and the laser A fourth matching frequency may be obtained for (L ₁ ) and high-Q micro resonator (M ₃ ). Other combinations are possible. Each high-Q micro resonator (M ₁ … M _N ) can provide the generation of one or multiple back propagation modes, respectively, at one of at least one matching frequency. In particular, as described above for the example with one laser (L ₁ ) and three high-Q micro resonators (M ₁ , M ₂ , M ₃ ), each of the high-Q micro resonators (M ₁ and M ₃ ) Generates one backpropagation mode, and the high-Q micro resonator (M ₂ ) can generate two backpropagation modes at each matched frequency. One or more back propagation modes (mode-s) are coupled back to multiple longitudinal mode lasers (L ₁ ) in the form of optical feedback (S ₁ … S _N ), one of the matched frequencies and the dominant longitudinal laser mode It is possible to provide optical feedback and redistribution of the power of multiple longitudinal mode lasers (L ₁ ), which are advantageous for each of the at least one dominant longitudinal laser mode at a reduced linewidth of. In particular, as described above for the example with one laser (L ₁ ) and three high-Q micro resonators (M ₁ , M ₂ , M ₃ ), the power of the multiple longitudinal mode laser (L ₁ ) is reduced. It can be advantageously redistributed to the four dominant longitudinal laser modes with reduced linewidths.

Figure 3 shows that multiple longitudinal mode lasers (L ₁ ) are simultaneously locked to several series high-Q micro resonators (M ₁ … M _N ), e.g., WGMs micro resonators via multiple coupling elements (C ₁ … C _N ). Another example of the case is schematically shown. Each high-Q micro-resonator (M ₁ … M _N ) is coupled to a bus waveguide and receives laser light 1 with a spectrum of multiple longitudinal modes. The tuning unit (TU) (not shown) consists of each resonant frequency of the high-Q mode of a plurality of high-Q micro resonators (M ₁ … M _N ) and at least one of the individual longitudinal modes to obtain at least one matching frequency. We can tune the spectrum of multiple longitudinal modes of laser light 1 to match each of the frequencies of. Each high-Q micro resonator (M ₁ … M _N ) can provide the generation of one or multiple back propagation modes, respectively, at one of at least one matching frequency. The backscattered light waves (S ₁ … S _N ) resonated from the high-Q micro resonators (M ₁ … M _N ) are at least one of the matching frequencies and one or more, respectively, at a reduced linewidth of the dominant longitudinal laser mode. It is possible to provide optical feedback and redistribution of the power of multiple longitudinal mode lasers (L ₁ ) in favor of the dominant longitudinal laser mode. Each of the light wave(s) (S ₁ … S _N ) can only resonate with one high-Q micro resonator to eliminate their interaction.

Figure 4 schematically shows another embodiment when multiple multi-longitudinal mode lasers (L ₁ … L _m ) are simultaneously locked to one high-Q micro resonator (M ₁ ), e.g., one WGM micro resonator. Explain. The laser light 1 can be combined and coupled to the high-Q micro resonator M ₁ via a coupling element C ₁ . The high-Q micro-resonator (M ₁ ) receives laser light (1) with a spectrum of multiple longitudinal modes. The tuning unit (TU) (not shown) has a laser light (1) to match each of the at least one frequency of the individual longitudinal mode with each resonant frequency of the high-Q micro-resonator (M ₁ ) to obtain at least one matching frequency. ), the spectrum of multiple longitudinal modes can be tuned. For example, 3 matching frequencies can be obtained for 3 lasers (L ₁ , L ₂ , L ₃ ) and 1 high-Q micro resonator (M ₁ ), where lasers L ₁ and high-Q micro The first matching frequency can be obtained for the resonator (M ₁ ), the second matching frequency can be obtained for the laser (L ₂ ) and the high-Q micro resonator (M ₁ ), and the laser (L ₃ ) and A third matching frequency can be obtained for the high-Q micro resonator (M ₁ ). Resonant backscattered light waves (S ₁ ) from the high-Q micro-resonator (M ₁ ) at the matched frequency provide optical feedback for each laser, and each dominant longitudinal laser mode at the matched frequency and reduced line width. Advantageously to multiple longitudinal mode lasers (L ₁ , L ₂ , L ₃ ) provide redistribution of the power of each.

Figure 5 shows a number of multiple longitudinal mode lasers (L ₁ … L _m ) through a coupling element (C _PN ) simultaneously locked to a number of parallel and series high-Q micro resonators (M _PN ), e.g. WGM micro resonators. It shows the method of another embodiment when it becomes. As in the above-described embodiments, each of the high-Q micro resonators (M _PN ) is a laser light (1) from a plurality of multiple longitudinal mode lasers (L ₁ … L _m ) having a spectrum of multiple longitudinal modes. ) Can be received. The tuning unit (TU) (not shown) has laser light to match each of the at least one frequency of the individual longitudinal mode with the respective resonant frequency of the high-Q micro resonator (M _PN ) to obtain at least one matching frequency. (1) The spectrum of multiple longitudinal modes can be tuned. Resonant backscatter from at least one of the matched high-Q micro-resonator in the frequency (M _PN) (S _PN) is at least one matching frequency one and the prevailing longitudinal laser modes, each laser respectively prevailing longitudinal direction at a reduced line width of the Mode advantageously can provide optical feedback and redistribution of the power of each of the multiple longitudinal mode lasers (L ₁ … L _m ).

The embodiment is not limited by the modifications shown in FIGS. 1-5. Other configurations based on combinations of one or a number of variations of FIGS. 2 to 4 are also possible. For example, the laser device may include several parallel components as shown in FIG. 2, each of which is a plurality of coupling elements (C ₁ … C _N ) as shown in FIG. It can contain multiple longitudinal mode lasers (L ₁ ) simultaneously locked to a series of high-Q micro-resonators (M ₁ … M _N ). In addition, the coupling element C may be configured in the form of a tapered optical fiber or waveguide. In such a case, as described above, one or more of the at least one multi-longitudinal mode laser may be optical feedback coupled to one or more of the at least one high-Q micro resonator via one of the aforementioned coupling elements. have.

In one embodiment, the tuning unit (TU) (see Fig. 1A) is a plurality of sub-units (TL and TM) that may each be associated with at least one laser (L) and at least one high-Q micro resonator (M). It may include, or it may be configured as a single unit each associated with at least one laser and at least one high-Q microresonator (see Fig. 1A). Also other configurations of the tuning unit (TU) may be possible. The tuning unit may be configured to control the parameters of the at least one laser, for example the injection current and/or temperature of the laser gain medium of the at least one laser. For example, the tuning unit may be configured to individually control the aforementioned parameters of each of the at least one multiple longitudinal mode laser. In addition, the tuning unit includes parameters of at least one high-Q micro resonator, e.g. temperature, external pressure applied to at least one high-Q micro resonator, at least one high-Q micro resonator if made of electro-optical material. It can be configured to control the electromagnetic field applied to it. For example, the tuning unit can be configured to individually control the parameters of each of at least one high-Q micro resonator. The tuning unit may have or be connected to measurement equipment such as a temperature sensor, a pressure sensor, an electromagnetic field sensor, and a current controller used for spectrum tuning. The tuning unit can further communicate with optical detectors, optical spectrum analyzers, electrical spectrum analyzers, oscilloscopes and measuring equipment for spectral conversion control such as their analogues, reference narrow linewidth lasers for measurement of dominant longitudinal mode linewidths, and the like. The tuning unit (TU) is also connected with heating elements, current controllers, pressure piezoelectric ceramics, control equipment such as radio frequency antennas or capacitor plates, and at least one high-Q micro-resonator and transmits an external electromagnetic field to change its resonant frequency. It may be connected to or include a waveguide. The aforementioned measurement and control equipment may be configured to measure and change the aforementioned parameters of at least one laser and/or at least one high-Q micro resonator. In one embodiment, the tuning unit tunes the spectrum of multiple longitudinal modes of the at least one laser to obtain a matching frequency and/or tunes the spectrum of the resonant frequency of the high-Q mode of the at least one high-Q micro resonator. There may be further provided a processor configured to provide analytical feedback between the hazard measurement and control equipment. The processor can be operably coupled to a computer control system that can be programmed to control the tuning unit in a predetermined manner to optimize operation.

In the embodiment shown in Figure 1a, when the laser device includes one laser (L) and one high-Q micro resonator (M), the tuning unit (TU) will be configured as shown in Figure 6a. I can. The tuning unit (TU) may include two sub-units (TL, TM), each associated with a laser (L) and a high-Q micro resonator (M) to control their parameters as mentioned above.

6B shows an example of a part of the configuration of the measurement equipment used to control the spectral transformation. The laser light from the multiple longitudinal mode Indium Phosphide (InP) laser diode (L) is collimated using a lens "Lens" (first along the laser beam in Fig. 6b), and is coupled like a glass internal total reflection coupling prism. It can be coupled to a magnesium fluoride (MgF2) high-Q micro resonator (M) through a ring element (C). The resonantly backscattered Rayleigh radiation returns to the multi-longitudinal mode diode laser (L) and can force the self-injection locking of the laser frequency to the resonant frequency of the high-Q microresonator (M). The output laser light with the output spectrum is collimated into a single mode fiber using two lenses (a second “Lens” and a third “Lens” along the laser beam in Fig. 6b), and with an optical spectrum analyzer (OSA), It can be analyzed on a photodiode (PD) with an oscilloscope (OSC) and a fast photodiode (FPD) with an electrical spectrum analyzer (ESA). The 50/50 beam splitter can be used to evenly split the output laser signal between the OSA and ESA. Sensitive oscilloscopes (OSCs) can accommodate, for example, about 1% of the laser energy for OSA using a 99/1 beam splitter, for example. The repetition rate of the soliton pulse can be monitored by a fast photodiode (FPD) and an electrical spectrum analyzer (ESA). The laser frequency detuning from optical resonance can be monitored on a photodiode (PD) with an oscilloscope (OSC). A narrow line width tunable fiber laser (FL) can be used to measure the heterodyne line width.

In one of the embodiments, the subunit TL of the tuning unit TU (as shown in Figs. 1A, 6A, 6B) is measured by a current sensor 1 and/or a temperature sensor 2 The generated data may be received and transmitted to the processor P. The subunit TM of the tuning unit TU may receive data measured by the pressure sensor 8, the temperature sensor 9, and/or the electromagnetic field sensor 10 and transmit the data to the processor P. The processor P also controls the spectral conversion (e.g., measuring the line width of the longitudinal mode dominant in the self-injection locking scheme), an optical spectrum analyzer (OSA), a photodiode (PD) with an oscilloscope (OSC), It can be configured to communicate with a high-speed photodiode (FPD) with an electrical spectrum analyzer (ESA) and a narrow line width laser reference laser (FL). In order to tune the spectrum of the multiple longitudinal mode laser L to obtain one or multiple matching frequencies, the processor P can provide analysis feedback between the measurement and control equipment. For example, the processor (P) transmits a control signal to the current controller (3) to change the laser injection current of the multiple longitudinal mode laser (L) associated therewith and/or the processor (P) A control signal can be transmitted to the heating element 4 to change the temperature of the laser active medium of the mode laser L. To tune the spectrum of the high-Q mode of the at least one high-Q micro-resonator (M) to obtain a matching frequency, the processor (P) sends a control signal to the pressing piezoelectric ceramic (5) to obtain the corresponding high-Q micro-resonator. By varying the pressure applied to the resonator M and/or the processor P can send a control signal to the heating element 6 to change the temperature of the high-Q micro-resonator M associated therewith. In addition, when the high-Q micro resonator (M) is made of electro-optical material, to adjust the spectrum of the high-Q mode of at least one high-Q micro resonator (M) to obtain one or multiple matching frequencies. , The processor P may transmit a control signal to the electromagnetic field controller 7 to change the electromagnetic field applied to the high-Q micro resonator M related thereto. The computer control system (CCS) can be programmed to control the tuning unit (TU) in a predetermined manner to optimize its operation.

In the embodiment shown in Fig. 2, the tuning unit comprises one sub-unit (TL) associated with a multiple longitudinal mode laser (L ₁ ) and N subunits associated with each high-Q micro resonator (M ₁ … M _N ). It can be configured to include a unit (TM). In the embodiment shown in Fig. 5, the tuning unit comprises M subunits (TL) associated with each of the multiple longitudinal mode lasers (L ₁ … L _m ) and P* associated with each high-Q micro resonator (M _PN ). It may be configured to include N subunits (TM). However, other configurations are possible. For example, in the embodiment of Fig. 2, the tuning unit may include two sub-units (TL and TM), and the sub-unit (TM) is associated with all high-Q micro resonators (M ₁ … M _N ). Can be.

In the above-described embodiment, the spectrum of multiple longitudinal modes of laser light is determined by means of a tuning unit (TU) (see Fig. 1) at least one multiple longitudinal mode laser L, e.g., individually at least one multiple longitudinal mode. One or more of each of the individual longitudinal modes of each laser can be slightly tuned to TL in the frequency domain by adjusting the laser injection current to achieve a match with the respective resonant frequency of the high-Q micro-resonator M. In Fig. 7, tuning the spectrum of multiple longitudinal modes of laser light is shown as a signal (solid line curve) from the photo detector D (see Fig. 1A). The transmission drops indicated on the signal are the resonance of the high-Q micro resonator. When the laser is locked to the resonant frequency mode of the microresonator, the laser frequency is pulled in the frequency sweep, resulting in a sharp edge of the resonance. Rayleigh backscatter propagating in the form of a half-propagation mode (mode -s) responsible for optical feedback and narrowing the laser spectrum when coupled from a high-Q microresonator is shown in the same Figure 7 (dotted line), and Rayleigh backscattering The power is increased by a factor of 100 to compare with the power of the same LD. The choice of resonant Rayleigh backscatter power can correspond to the resonant frequency of the high-Q micro resonator when the laser frequency is adjusted by the laser injection current. When the laser injection current is not swept and the frequency of one of the longitudinal laser modes is tuned to match the resonant frequency of the high-Q microresonator, the laser longitudinal mode competition process can be initiated in the resonant optical feedback condition.

The result of performing the mode competition under the optical feedback condition is shown in FIG. 8, which includes a pre- including a plurality of longitudinal modes within a range of 1535 nm to 1560 nm at intervals of about 0.14 nm (corresponding to ~ 17 GHz in the frequency domain). An example of converting the spectrum of a free-running multiple longitudinal mode near infrared laser (shown on the left) to an output spectrum with one dominant longitudinal mode (shown on the right) is shown. When one frequency of one individual longitudinal mode in the multiple longitudinal mode spectrum coincides with one resonant frequency of a high-Q microresonator, the power of many longitudinal modes is one further narrowed by the high-Q microresonator. Advantageously redistributed to the predominant longitudinal laser mode of, its power can be greatly increased by several thousand times (Fig. 8).

In one embodiment where the laser injection current is not swept, the spectrum of the multiple longitudinal modes of the laser light is at least one multiple longitudinal mode laser, e.g., each of the at least one multiple longitudinal mode laser individually controls the temperature of the laser active medium. By varying it can be tuned by the adjustment unit (TU) to lead to a change in its refractive index, thus leading to a change in the spacing of the longitudinal mode in the frequency domain and a change in the frequency of each of the individual longitudinal modes.

In another embodiment, when the laser injection current is not swept and the temperature of the laser active medium is stable, the tuning unit (TU) is to tune the resonant frequency of the high-Q mode of at least one high-Q micro resonator (M). Can be configured to further tune at least one matching frequency under conditions of optical feedback. The tuning unit can control the spacing of the high-Q mode in the frequency domain by controlling the temperature and/or external pressure applied to the high-Q microresonator, and each of the individual high-Q modes of at least one high-Q microresonator. The frequency can be controlled. Both options individually vary the refractive index and/or dimensions of each of at least one high-Q micro resonator, e.g. at least one high-Q micro resonator, thus varying the resonant frequency and/or spacing of the high-Q mode. I can make it.

In another embodiment, at least one high-Q micro resonator may be made of an electro-optical material whose refractive index changes in response to an applied electromagnetic field, and the tuning unit (TU) is at least one high-Q micro resonator, e.g. , It may be further configured to control an individually applied electromagnetic field of each of the at least one high-Q micro resonator. Changing the refractive index of the at least one high-Q micro resonator changes the resonant frequency, where the tuning unit is the resonant frequency of the at least one high-Q micro resonator so that it can further tune the at least one matching frequency under optical feedback conditions. Can be tuned. As examples of electro-optical materials for the manufacture of high-Q microresonators, lithium niobate and indium phosphide can be mentioned.

9A-9C show that at least one high-Q microresonator is locked when each of one or several frequencies of the individual longitudinal modes of at least one laser coincides with each resonant frequency of at least one high-Q microresonator. It shows the result of transforming the spectrum of at least one multi-longitudinal mode laser. For Figures 9B and 9C, the longitudinal mode competition in the light feedback condition provides for simultaneous generation of multiple narrow laser lines.

Figure 9a shows the generation of a single frequency when one frequency of the individual longitudinal modes of at least one multi-longitudinal mode laser L coincides with one resonant frequency of at least one high-Q micro resonator M . In this case, an output laser light having an output spectrum in one dominant longitudinal laser mode can be produced by the laser device. Figure 9b shows the generation of two frequencies when the two frequencies of the individual longitudinal modes of at least one multiple longitudinal mode laser (L) coincide with the two resonant frequencies of at least one high-Q micro resonator (M). do. In this case, an output laser light having an output spectrum in two dominant longitudinal laser modes can be generated by the laser device. Figure 9c is a diagram of a four-frequency lasing when four frequencies of the individual longitudinal modes of at least one multiple longitudinal mode laser (L) coincide with the four resonant frequencies of at least one high-Q micro-resonator (M). Shows an example. In this case, light having an output spectrum in the four dominant longitudinal laser modes, output laser light is generated by the laser device. As described above, as a result of mode competition in the condition of resonant optical feedback, the power of at least one multiple longitudinal mode laser can be advantageously redistributed to one or multiple narrow laser lines.

9B and 9C, coupling at least one multi-longitudinal mode laser to at least one high-Q micro resonator, and at least one high-Q micro resonator to obtain multiple matching frequencies. As a result of tuning the spectrum of multiple longitudinal modes so that each resonant frequency and each of the multiple frequencies of the individual longitudinal modes match, the multiple individual longitudinal modes of the multi-longitudinal mode spectrum are at the narrower linewidth of the dominant longitudinal laser mode. It can be converted into a number of dominant longitudinal modes.

This embodiment provides great flexibility of multiple narrow linewidth lasing at different frequencies required for a particular application, which means that the generation of multiple narrow laser lines is different, as shown in Figs. This is because it can represent different high-Q micro resonators. Proper selection of multiple longitudinal mode lasers and high-Q micro-resonators with specific frequencies to tune allows engineering of the output spectrum consisting of narrow laser lines at any frequency required for a specific application. In one of the embodiments, one or more dominant longitudinal laser modes can be coupled from the high-Q micro-resonator M via an additional coupling element C2 (see FIG. 1B) that is a total internal reflection prism. In other embodiments, one or more of the at least one high-Q micro resonator (M) is one additional coupling element in the form of a tapered optical fiber or waveguide used in place of the total internal reflection prism schematically shown in FIG. C2) can be provided. The use of an additional coupling element can significantly improve the spectral purity of the output spectrum of the output laser light including the dominant longitudinal laser mode by filtering out non-resonant portions of the output spectrum generated by the laser device. The spectral purity of the output spectrum is often required for many microphotonic applications. In Fig. 1b, the laser light 1 and laser light 2 with the output spectrum are coupled from the high-Q micro-resonator M through a coupling element C (total internal reflection prism) as shown on the right. , The laser light 1 and the laser light 2 may comprise a weak non-resonant laser longitudinal mode. An additional coupling prism (C2) can provide coupling from a high-Q micro-resonator (M) a laser light (3) having a pure spectrum consisting of only the dominant longitudinal laser mode without a non-resonant portion of the output laser light ( As shown on the left). In other words, the laser light 3 may have a dominant longitudinal laser mode with the higher side mode suppression ratio (SMSR) parameter described above compared to the laser light 2. In this case, the SMSR may be in the range of approximately 40-70 dB, for example in the range of approximately 50-70 dB. For example, about 60dB can often provide a sufficient side-mode suppression ratio value for the purpose of this application.

Another group of embodiments includes deformation when at least one high-Q microresonator is made of a material having an intensity dependent refractive index, wherein the laser device is further configured to generate at least one optical frequency comb, wherein at least one dominant When the longitudinal laser mode has a power greater than the pump threshold of optical frequency comb generation, each of the at least one optical frequency comb may be parametrically generated by one of the at least one dominant longitudinal laser mode. There are many examples of materials with an intensity-dependent refractive index such as transparent fluoride over a broad spectral range: calcium fluoride, barium fluoride and magnesium fluoride. Also worth mentioning are quartz, silicon, silicon nitride, and diamond.

Figure 10a shows a single dominant longitudinal direction with a reduced linewidth as described above, since only one frequency of the individual longitudinal mode coincides with one resonant frequency of the high-Q magnesium fluoride WGM microresonator to obtain one matching frequency. An example of converting the spectrum of a multiple longitudinal mode laser locked to a high-Q magnesium fluoride WGM microresonator generating laser mode is shown. As in the optical method of FIG. 1A, due to mode competition in the optical feedback condition, the laser power was redistributed in favor of one dominant longitudinal laser mode at the matched frequency. The side mode suppression ratio is about 30dB. Next, in Fig. 10b, the output laser light having an output spectrum with one dominant longitudinal laser mode effectively coupled to a high-Q microresonator having a power level higher than the pump threshold is parametrically dissipative. It can generate a kerr soliton comb (DKS). The Kersoliton comb is an optical frequency comb having a plurality of spectral modes spaced apart by a fixed value of a frequency different from that of the laser longitudinal mode. 10B shows the signal immediately after the coupling prism C in the optical method of FIG. 1A. The signal combines the laser light 2 coming from the high-Q micro resonator M and the non-resonant laser light 2 passed from the multiple longitudinal mode laser L through the coupling prism C. In the above-described embodiment, when a cleared optical frequency comb is required, an additional coupling element C2 can be used to filter the non-resonant portion of the output spectrum (Fig. 1B).

The specific measurement data shown in FIGS. 10A and 10B correspond to a free spectral range (FSR) of ~ 12.5 GHz (inverse of the pulse round trip time in the micro resonator), corresponding to a high-diameter of about 5.5 mm and a corner curvature radius of about 500 μm Q magnesium fluoride (MgF2) was obtained using a WGM micro resonator. Magnesium fluoride refractive index depends on the laser intensity allowing the generation of DKS. The high-Q micro resonator was fabricated by precise single point diamond turning of bulk crystals. An ultrahigh intrinsic Q-factor exceeding 10 ⁹ was achieved by polishing with a diamond slurry. The laser diode used to obtain the specific measurement data in FIGS. 10A and 10B is a longitudinal mode f = 17.68 GHz around the center wavelength of about 1,535 nm and dozens of longitudinal modes covering ~ 10 nm with a maximum output power of about 200 mW. It has a light spectrum composed of. The intensity of the laser gain area is approximately uniformly distributed between the lines. By gradually changing the injection current, one of the longitudinal laser modes has become one dominant longitudinal mode in which the line width is reduced and matched with the resonance mode of the microresonator to obtain optical feedback.

Next, by gradually detuning the diode laser frequency on the low-frequency side with the injection current, but keeping it in a locked state, the system is a soliton comb system with a very characteristic sech2(x) envelope (Fig. 10b) (mainly single -Solitone) could be switched smoothly. The soliton comb has a span of ~30nm with a line spacing of about 12.5GHz, which corresponds to the free spectrum range of the microresonator. An additional residual laser line separated by about 17.68 GHz can be seen in the optical spectrum and, although weak, can be filtered in the drop port configuration using an additional coupling element (see Figure 1b).

Another embodiment includes a modification when multiple optical frequency combs can be produced by multiple dominant longitudinal laser modes. 11A shows two optical frequency combs generated simultaneously in the case of a multiple longitudinal mode laser diode locked to a high-Q magnesium fluoride WGM with the generation of a dominant longitudinal laser mode pumping a parametrically generated frequency comb (Fig. It shows the light spectrum of the curve in the middle part of 11a and the curve in the other part). First, the laser light with the spectrum of multiple longitudinal modes is tuned to match the two frequencies of the longitudinal mode with the two resonant frequencies of the high-Q micro resonator to obtain two matched frequencies. The high-Q microresonator receives a separate longitudinal mode of laser light at a matched frequency corresponding to the resonant frequency to provide optical feedback due to Rayleigh backscattering. Mode competition in optical feedback conditions can lead to redistribution of laser power in favor of the two dominant longitudinal modes at the two matching frequencies. Optical frequency combs can be generated when the power of the dominant mode exceeds the pump threshold. Each comb is a plurality of narrow spectral modes spaced apart by a fixed value of a frequency different from that of the laser longitudinal mode. 11B shows the spectrum of the narrow mode radio frequency beating of the comb as measured using a high speed photodiode and an electrical spectrum analyzer. There are two beatnotes that correspond to the comb teeth. The line width of Bit Note is lower than 1 kHz, which shows that the width of the frequency comb mode is narrow. The narrow spectral modes of the two combs were separated by different frequency values by a difference of about 10 MHz.

In one of the embodiments, at least one high-Q microresonator can be fabricated on a semiconductor chip (silicon nitride or silicon-on insulator) with at least one multi-longitudinal mode laser. Examples of such hybrid integration of silicon photonic resonators and III-V gain materials for the near-infrared range have been successful. Thus, in one of the embodiments, at least one multiple longitudinal mode laser and at least one high-Q micro resonator can be made on the same chip using microlithography. 12A, 12B schematically show a chip comprising mirrors M1, M2 and one high-Q micro-resonator M, e.g. one multiple longitudinal mode laser L with one WGM micro-resonator do. In the plan view shown in Fig. 12A, a multi-longitudinal mode laser (L) integrated in a III-V gain material 11, for example indium phosphide (InP), is formed through a special coupler 12 through a silicon/silicon nitride (Silicon). / Si3N4) (13) is coupled to the waveguide. The coupler 12 interconnects the bonded silicon/silicon nitride 13 layer (see side view in Fig. 12b) and the III-V material 11 layer comprising a bus waveguide and a high-Q micro resonator M. The coupler 12 is a vertical connection portion of a tapered waveguide (see variant I of FIG. 12B, which shows an enlarged view of the tapered waveguide 14) or a Bragg grid vertical connection portion of a waveguide made of another material (an enlarged view of the grating 15). See variant II of FIG. 12B shown). In the rest, multiple longitudinal mode lasers (L) and high-Q micro-resonators (M) made on a chip can operate in the same manner as the laser device of Fig. 1A, which includes a tuning unit (TU) operation (Fig. 12A). , Not shown in Figure 12b). In some embodiments, the at least one multi-longitudinal mode laser is one of the at least one high-Q micro-resonator via a coupling element (C) configured as a waveguide located at a sub-wavelength distance from the at least one high-Q micro-resonator. It can be optically feedback coupled to one or more. The additional coupling element C2 shown by the dotted border in FIG. 12A can be used optionally, by coupling one or more of the dominant longitudinal laser modes generated in one or more of at least one high-Q micro-resonator. It can be configured to filter out non-resonant portions of the output spectrum. In the case of a high-Q microresonator and multiple longitudinal mode lasers manufactured on one semiconductor chip, some individual elements of the subunits (TL and TM) related to the laser and microresonators may be correspondingly integrated on the same chip. . Such elements may be micro-resonators or metal micro-heaters for tuning the active medium temperature of the laser, photo detectors for measuring output signals, and the like.

The method of converting the laser spectrum includes at least one multiple longitudinal mode laser (L) for generating laser light having a spectrum of multiple longitudinal modes, and at least one multiple longitudinal mode laser (L) in FIGS. ), at least one high-Q microresonator (M) optically feedback-coupled.

In the first step of the method, laser light having a spectrum of multiple longitudinal modes can be produced by at least one multiple longitudinal mode laser (L).

In the second step of the method, the spectrum of the multiple longitudinal modes of the laser light is each and at least one frequency of the respective longitudinal modes of the at least one multiple longitudinal mode laser L in order to obtain at least one matching frequency. Each resonant frequency of at least one high-Q micro resonator (M) optically feedback coupled to one multiple longitudinal mode laser (L) can be tuned to match.

In a third step of the method, an output laser light having an output spectrum each having at least one dominant longitudinal laser mode at one of the at least one matching frequency and at a reduced linewidth of the dominant longitudinal laser mode can be coupled. have.

It should be noted that this method may involve additional steps.

For example, if at least one high-Q micro-resonator (M) is made of a material with an intensity-dependent refractive index, the method is that at least one dominant longitudinal laser mode exceeds the pump threshold of optical frequency comb generation. In the case of having a power of at least one dominant longitudinal laser mode, the step of parametrically generating at least one optical frequency comb may be further included.

The method comprises the steps of tuning the spectrum of the longitudinal mode both by changing the spacing of the longitudinal modes in the frequency domain, and changing the frequency of each of the individual longitudinal modes of at least one multiple longitudinal mode laser (L). It may further include.

The method may further comprise providing optical feedback to the at least one multiple longitudinal mode laser (L) by generating at least one back propagation mode each at one of the at least one matching frequency.

This method controls the injection current of at least one multiple longitudinal mode laser and/or the temperature of the laser active medium of each of at least one multiple longitudinal mode laser (L) individually, for example individually By doing so, it may further include tuning the spectrum of the multiple longitudinal modes.

This method may further include tuning the resonant frequency of each of the at least one high-Q micro resonator (M) by changing the interval of the high-Q mode in the frequency domain and changing the resonant frequency of each high-Q. .

The method comprises controlling the temperature of at least one high-Q micro resonator and/or the external pressure applied individually to at least one high-Q micro resonator (M), e.g., each of at least one high-Q micro resonator. May contain more.

If one or several of the at least one high-Q micro resonator (M) is provided with an additional coupling element (C2), this method can be used with one or more dominant longitudinal laser modes or one or more dominant laser modes and output. It may further comprise coupling one or multiple optical frequency combs from one or multiple of the at least one high-Q micro-resonator via an additional coupling element to filter out non-resonant portions of the spectrum.

If at least one high-Q micro resonator (M) is made of an electro-optical material that changes the refractive index in response to an electromagnetic field applied to the at least one high-Q micro resonator, this method is (M) Each, for example, may further comprise the step of controlling an electromagnetic field individually applied to each of the at least one high-Q micro-resonator.

A method of operating the laser device includes at least one multiple longitudinal mode laser (L) for generating laser light having a spectrum of multiple longitudinal modes, as shown in FIGS. 1 to 6, and at least one multiple species. At least one high-Q micro-resonator (M) optically feedback-coupled to the directional mode laser (L), and a tuning unit (TU) for tuning the spectrum of multiple longitudinal modes of the laser light will be described.

In the first step of the method, the spectrum of the multiple longitudinal modes of the laser light is tuned by a tuning unit (TU) to obtain at least one matching frequency at least of the individual longitudinal modes of the at least one multiple longitudinal mode laser. Each of one frequency and each resonant frequency of at least one high-Q micro resonator M are matched.

In a second step of the method, an output laser light having an output spectrum having at least one dominant longitudinal laser mode each at one of the at least one matched frequency and at a reduced linewidth of the dominant longitudinal laser mode is coupled from the device. Ring.

It should be noted that the examples are described with reference to different subjects. However, those skilled in the art will, unless otherwise notified, in addition to the combinations of features pertaining to one type of subject matter, any combination between features relating to different subjects that may be disclosed in the present application is contemplated as described above and below. Will collect from the description. However, all functions can be combined to provide synergies beyond the simple sum of functions.

While the embodiments have been shown and described in detail in the drawings and the foregoing description, such examples and descriptions are to be regarded as illustrative or not limiting. The claims are not limited to the disclosed embodiments. Other modifications to the disclosed embodiments may be understood and influenced by those skilled in the art in carrying out the claimed invention from the drawings, the disclosure, and the study of the dependent claims.

In the claims, the word "comprising" does not exclude other elements or elements, and elements do not exclude a plurality. The fact that certain measures have been cited in different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

C ... coupling element D... photodetector
L: Multiple longitudinal mode laser
M: high-Q micro resonator
S...backscattered light wave TL,TM...sub unit
TU: Tuning units 1,2,3...laser light

Claims (32)

At least one multiple longitudinal mode laser for generating laser light having a spectrum of multiple longitudinal modes;
At least one high-quality coefficient (high-Q) microresonator optically feedback-coupled to the at least one multiple longitudinal mode laser;
Of the laser light to match the resonant frequency of each of the at least one high-Q micro-resonator with each of the at least one frequency of the respective longitudinal mode of the at least one multi-longitudinal mode laser to obtain at least one matching frequency. It includes; a tuning unit for tuning the spectrum of the multiple longitudinal mode,
And at least one of the matching frequencies and at a reduced linewidth of the dominant longitudinal laser mode, respectively, to couple output laser light having an output spectrum with at least one dominant longitudinal laser mode. The method of claim 1,
The at least one high-Q micro resonator is made of a material having an intensity-dependent refractive index,
The laser device is provided to generate at least one optical frequency comb, and
Each of the at least one optical frequency comb is parametric by one of the at least one dominant longitudinal laser mode when the at least one dominant longitudinal laser mode has a power greater than the pump threshold of optical frequency comb generation. Laser device, characterized in that produced in a manner. The method of claim 1 or 2, wherein the tuning unit is arranged to change the spacing of the longitudinal mode in the frequency domain and to change the frequency of each of the individual longitudinal modes of the at least one multiple longitudinal mode laser. Laser device, characterized in that. The method of claim 1 or 2, wherein the at least one high-Q micro-resonator generates at least one reverse propagation mode at one of the at least one matched frequency to light the at least one multiple longitudinal mode laser. Laser device, characterized in that provided to provide feedback. 3. A laser device according to claim 1 or 2, wherein the at least one multi-longitudinal mode laser comprises an electrically powered semiconductor laser diode. The laser device according to claim 1 or 2, wherein the at least one multiple longitudinal mode laser and the at least one high-Q micro resonator are made on the same chip using microlithography. The method of claim 1 or 2, wherein the tuning unit comprises an injection current of the at least one multiple longitudinal mode laser and/or the at least one multiple longitudinal mode laser or individually the at least one multiple longitudinal mode laser A laser device, characterized in that it is arranged to control the temperature of each laser active medium. The method of claim 1 or 2, wherein the at least one multi-longitudinal mode laser comprises the at least one multi-longitudinal mode laser by coupling the light scattered from the at least one high-Q micro-resonator to the at least one multi-longitudinal mode laser. Laser device, characterized in that the optical feedback coupling to the high-Q micro resonator of. The method of claim 1 or 2, wherein one or more of the at least one multiple longitudinal mode laser is optically feedback coupled to one or more of the at least one high-Q micro resonator via a coupling element. Laser device, characterized in that. The laser device of claim 9, wherein the coupling element comprises at least one of a total internal reflection prism, a tapered optical fiber and a waveguide. 3. Laser device according to claim 1 or 2, characterized in that one or more of said at least one high-Q micro-resonator is provided with an additional coupling element. 12. The method of claim 11, wherein the additional coupling element is to filter out one or a plurality of dominant longitudinal laser modes generated in one or more of the at least one high-Q microresonator or non-resonant portion of the output spectrum. A laser apparatus, characterized in that it is arranged to couple one or more dominant longitudinal laser modes and one or more optical frequency combs generated in one or more of said at least one high-Q micro-resonator. The laser device of claim 2, wherein the at least one optical frequency comb is a dissipating Kerr soliton soliton optical comb. The method according to claim 1 or 2, wherein the tuning unit changes the high-Q mode of the high-Q mode in the frequency domain and changes the resonant frequency of each high-Q mode. Laser device, characterized in that further configured to tune the resonant frequency of the mode. The method of claim 1 or 2, wherein the tuning unit is a temperature of the at least one high-Q micro resonator and/or each of the at least one high-Q micro resonator or the at least one high-Q micro resonator individually. Laser device, characterized in that provided to control the external pressure applied to. The method of claim 1 or 2, wherein the at least one high-Q micro resonator is made of an electro-optical material that changes the refractive index in response to an electromagnetic field applied to the at least one high-Q micro resonator,
And the tuning unit is further configured to control an electromagnetic field individually applied to each of the at least one high-Q micro resonator or the at least one high-Q micro resonator. The laser device of claim 1 or 2, wherein the at least one high-Q micro resonator comprises a WGM micro resonator. Generating laser light having a spectrum of multiple longitudinal modes by means of at least one multiple longitudinal mode laser;
At least one high optically feedback coupled each of the at least one frequency of the respective longitudinal mode of the at least one multi-longitudinal mode laser to the at least one multi-longitudinal mode laser to obtain at least one matched frequency. -Tuning the spectrum of multiple longitudinal modes of the laser light to match each resonant frequency of the Q micro-resonator;
Coupling an output laser light having an output spectrum each having at least one dominant longitudinal laser mode at one of the at least one matching frequency and at a reduced linewidth of the dominant longitudinal laser mode; Conversion method. The method of claim 18,
The at least one high-Q micro resonator is made of a material having an intensity-dependent refractive index,
The method comprises, when the at least one dominant longitudinal laser mode has a power exceeding a pump threshold of optical frequency comb generation, the at least one optical frequency comb is broken by each of the at least one dominant longitudinal laser mode. A method of converting a laser spectrum, further comprising generating in a metric manner. 20. The method of any one of claims 18 and 19, wherein the spectrum of the multiple longitudinal modes changes the spacing of the longitudinal modes in the frequency domain and the frequency of each of the respective longitudinal modes of the at least one multi-longitudinal mode laser. Laser spectrum conversion method, characterized in that tuned by changing the. The method of any one of claims 18 and 19, wherein the at least one high-Q micro-resonator generates at least one reverse propagation mode each at one of the at least one matching frequency, thereby generating the at least one multiple longitudinal mode. A method of converting a laser spectrum, characterized in that it is arranged to provide optical feedback to the laser. The method according to any one of claims 18 and 19, wherein the spectrum of the multiple longitudinal modes is an injection current of the at least one multiple longitudinal mode laser and/or the at least one multiple longitudinal mode laser or individually the A method of converting a laser spectrum, characterized in that the at least one multiple longitudinal mode laser is tuned by controlling the temperature of each laser active medium. The laser of claim 21, wherein the at least one reverse propagation mode coupled back to the at least one multiple longitudinal mode laser is generated due to resonant Rayleigh scattering in the at least one high-Q microresonator. Spectral conversion method. The method of any one of claims 18 and 19, wherein one or more of the at least one multi-longitudinal mode laser is optically fed back to one or more of the at least one high-Q micro resonator via a coupling element. Laser spectrum conversion method, characterized in that coupled. 25. The method of claim 24, wherein the coupling element comprises at least one of a total internal reflection prism, a tapered optical fiber and a waveguide. The method according to any one of claims 18 and 19,
A method of converting a laser spectrum, characterized in that an additional coupling element is provided to one or more of said at least one high-Q micro resonator. 27. The additional coupling element of claim 26, wherein one or more dominant longitudinal laser modes or the one or more dominant longitudinal laser modes and one or more optical frequency combs filter out non-resonant portions of the output spectrum. And coupled from one or more of the at least one high-Q micro resonator through. The method of any one of claims 18 and 19, wherein the resonant frequency of the high-Q mode of the at least one high-Q microresonator changes the interval of the high-Q mode in the frequency domain, and each of the high-Q modes Laser spectrum conversion method, characterized in that tuned by changing the resonance frequency of. The method of any one of claims 18 and 19, wherein the method comprises a temperature of the at least one high-Q micro resonator and/or the at least one high-Q micro resonator or the at least one high-Q micro resonator. Controlling the external pressure applied individually to each of the laser spectrum conversion method. The method according to any one of claims 18 and 19,
The at least one high-Q micro resonator is made of an electro-optical material that changes a refractive index in response to an electromagnetic field applied to the at least one high-Q micro resonator,
The method further comprises controlling an electromagnetic field individually applied to each of the at least one high-Q micro resonator or the at least one high-Q micro resonator. 20. The method of any one of claims 18 and 19, wherein the at least one high-Q micro resonator comprises a WGM micro resonator. In the method of operating the laser device according to any one of claims 1 to 17,
In order to obtain at least one matched frequency, the at least one frequency of the laser light to match each of the at least one frequency of the respective longitudinal mode of the at least one multiple longitudinal mode laser with the respective resonant frequency of the at least one high-Q micro resonator. Tuning the spectrum of multiple longitudinal modes;
Coupling output laser light having an output spectrum each having at least one dominant longitudinal laser mode at a reduced linewidth of said at least one matching frequency and said dominant longitudinal laser mode. .

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