WO2021013166A1 - 基于法布里波罗光腔的外腔激光器 - Google Patents

基于法布里波罗光腔的外腔激光器 Download PDF

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WO2021013166A1
WO2021013166A1 PCT/CN2020/103422 CN2020103422W WO2021013166A1 WO 2021013166 A1 WO2021013166 A1 WO 2021013166A1 CN 2020103422 W CN2020103422 W CN 2020103422W WO 2021013166 A1 WO2021013166 A1 WO 2021013166A1
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optical cavity
cavity
polarization
laser
band
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PCT/CN2020/103422
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French (fr)
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梁伟
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梁春
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
    • H01S5/14—External cavity lasers
    • H01S5/141—External cavity lasers using a wavelength selective device, e.g. a grating or etalon
    • H01S5/142—External cavity lasers using a wavelength selective device, e.g. a grating or etalon which comprises an additional resonator
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
    • H01S5/14—External cavity lasers

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  • This application relates to the laser field, for example, to an external cavity laser based on a Fabry Perot cavity.
  • the phase noise or line width of the laser is directly related to the quality factor (hereinafter referred to as the Q value) of the laser cavity.
  • Semiconductor lasers usually use the working medium, that is, the cleavage plane of the semiconductor crystal, as the resonant cavity. However, due to the material characteristics and crystal forming process, the Q value is usually low.
  • the first type is to use an external cavity feedback element for optical feedback to increase the reflectivity of the axial light, so that the overall Q value of the composite optical cavity composed of the laser and the external cavity feedback element is improved.
  • Figures 1 to 2 describe two typical methods of this type of external cavity feedback scheme (Optics Letters/Vol.13, No.10/October 1988 page 826).
  • the external cavity feedback element used in Figure 1 is a grating.
  • the external cavity feedback element used in Figure 2 is a mirror, and it shows that an interference filter is set between the laser and the mirror to filter through interference
  • the rotation of the sheet allows a single selection of multiple longitudinal modes.
  • This kind of scheme essentially increases the Q value of the composite optical cavity by lengthening the optical cavity and reflectivity to reduce laser noise, and cooperates with the grating or filter to realize the selection and switching of a single longitudinal mode.
  • This type of solution can realize lasers with a laser linewidth ranging from a few kHz to a few hundred kHz, but it is difficult to break through KHz and below.
  • the reason is that the Q value of a composite optical cavity composed of a grating or a single mirror is still low.
  • the Q value of the interference filter is also very low.
  • the second type of scheme is to use electrical negative feedback to suppress laser frequency noise.
  • Figure 4 shows a typical way of this type of method (Am.J.Phys.,Vol.69,No.1,January 2001).
  • This type of method is usually called the Pound-Drever-Hall (PDH) method, which first requires an optical cavity with an ultra-high Q value to measure the frequency noise of the laser.
  • Fabry Perot optical cavity FabryPerot, hereinafter referred to as F-P optical cavity
  • F-P optical cavity Fabry Perot optical cavity
  • F-P optical cavity is currently the best Q value and stability of a variety of optical cavities, has the longest research history, and is commonly used as the optical cavity of the PDH method.
  • F-P optical cavity Fabry Perot optical cavity
  • FIG. 5 is an exemplary implementation of using an F-P optical cavity for optical feedback.
  • Such a design can greatly simplify the entire system, and at the same time avoid the defect that electrical feedback cannot effectively suppress high-frequency laser noise.
  • Due to the extremely high specular reflectivity of the F-P optical cavity its resonance mode is always perpendicular to the mirror surface at the mirror surface. To efficiently couple the laser into the optical cavity, it must be incident perpendicular to the mirror surface. In this mode, at the F-P optical cavity, there are two types of optical feedback from the direct reflection from the mirror 1 and from the optical cavity, and the mode competition between these two feedbacks will seriously affect the stability of the laser.
  • This application provides an external cavity laser based on the Fabry Perot F-P optical cavity.
  • the laser of the present application directly uses the FP optical cavity for optical feedback, which can deal with the mode competition between the reflected light of the first mirror and the feedback light of the FP optical cavity, and at the same time, it can realize the laser frequency control in a larger range. High-speed continuous modulation.
  • An embodiment provides an external cavity laser based on a Fabry-Perot FP optical cavity, which includes a laser light source, a first lens, and an FP optical cavity sequentially arranged along the laser emission direction; wherein the FP optical cavity is reflected by the first The mirror and the second mirror constitute;
  • the optical path between the laser light source and the FP optical cavity is further provided with a polarization splitting element and a first polarization adjusting element in sequence along the laser emission direction; the polarization splitting element only allows light of a specific polarization state to pass through. Separate the light of other orthogonal polarization states; the first polarization adjustment element can change the polarization state of the light passing through the first polarization adjustment element twice to another orthogonal polarization state, the FP optical cavity There is also a second polarization adjusting element inside, or the first reflector and the second reflector are made of a material with birefringence effect coated with a highly reflective film.
  • An embodiment provides an external cavity laser based on a Fabry-Perot FP optical cavity, which includes a laser light source, a first lens, and an FP optical cavity sequentially arranged along the laser emission direction; wherein the FP optical cavity is reflected by the first The mirror and the second mirror constitute;
  • the optical path between the laser light source and the FP optical cavity is further provided with a polarization splitting element and a first polarization adjusting element in sequence along the laser emission direction; the polarization splitting element only allows light of a specific polarization state to pass through. Separate light in other orthogonal polarization states; the first polarization adjustment element can change the polarization state of the light that passes through the first polarization adjustment element twice to another orthogonal polarization state;
  • a second polarization adjustment element is provided downstream of the F-P optical cavity, and an external mirror is also provided downstream of the second polarization adjustment element.
  • Fig. 1 is a schematic diagram of optical feedback using gratings in related technologies
  • Figure 2 is a schematic diagram of using a mirror to perform optical feedback in the related art
  • Figure 3 is a schematic diagram of selective generation of single-frequency laser based on two interference filters in the related art
  • Fig. 4 is a schematic diagram of using an electrical negative feedback method to suppress laser frequency noise in the related art
  • FIG. 5 is a schematic diagram of directly using F-P optical cavity for optical feedback generation mode competition in related technologies
  • FIG. 6A is a schematic diagram of processing competition in F-P optical cavity direct optical feedback mode provided by this application.
  • FIG. 6B is a schematic diagram of the first improvement of the solution shown in FIG. 6A;
  • FIG. 6C is a schematic diagram of a second improvement to the scheme shown in FIG. 6A;
  • Figure 7 is a schematic diagram of the principle of frequency locking of the F-P optical cavity to the semiconductor laser
  • FIG. 8 is a schematic diagram of the gain curve of the semiconductor gain chip and the longitudinal mode spectrum line of the F-P optical cavity;
  • Figure 9A is a schematic diagram of using a gain chip and a high-Q F-P optical cavity to achieve ultra-narrowband laser and large-range continuous frequency modulation;
  • FIG. 9B is a schematic diagram of the first improvement of the solution shown in FIG. 9A;
  • FIG. 9C is a schematic diagram of a second improvement to the scheme shown in FIG. 9A;
  • Figure 10 is a schematic diagram of the composite spectrum of the gain curve, the longitudinal mode of the F-P optical cavity, and the bandpass curve of the interference filter;
  • FIG. 11 is a schematic diagram of using a birefringent crystal to replace a polarization beam splitting prism to achieve polarization beam splitting;
  • Fig. 12 is a schematic diagram of composite mode selection and frequency modulation of a band-pass filter with a periodic band-pass curve and an F-P optical cavity longitudinal mode.
  • 1 is a semiconductor laser
  • 2 is the first lens
  • 3 is a polarization beam splitter
  • 4 is a 1/4 ⁇ wave plate
  • 5 is the first mirror
  • 6 is the second mirror
  • 7 is a birefringent glass
  • 8 Is a phase shifter
  • 9 is a piezoelectric ceramic
  • 10 is an external mirror
  • 11 is an FP optical cavity
  • 12 is a gain chip
  • 13 is an interference filter
  • 14 is a second lens
  • 15 is a birefringent crystal.
  • the FP optical cavity 11 with a higher Q value is used as the external cavity or the ultra-narrowband filter in the external cavity, and its ultra-fine wavelength selective feedback is used.
  • the laser light emitted by the laser light source is collimated by the first lens 2 and then vertically directed to the F-P optical cavity 11, so that the laser light can be efficiently coupled into the F-P optical cavity 11, and is fed back to the laser light source after multiple reflections in the cavity.
  • this application has also made the following design.
  • a polarization splitting element and a first polarization adjusting element are sequentially arranged along the laser emission direction.
  • the polarization beam splitting element only allows light of a specific polarization state to pass through, and separates other orthogonal polarized light; for example, only allows P-polarized light to pass through but separates S-polarized light or vice versa.
  • the polarization beam splitter element may be a polarization beam splitter element that depends on a coating or a micro-nano structure, such as a polarization beam splitter (PBS), a 45 degree polarization beam splitter, and a Brewster angle polarization beam splitter, etc.
  • PBS polarization beam splitter
  • the polarization splitting element can also be an element that relies on the birefringent crystal effect, such as Glan-Taylor polarizer, Glan-Tompson polarizer, Wollaston polarizer, Rochon prism and so on.
  • the first polarization adjustment element can change the polarization state of the light passing through it twice between the two orthogonal polarization states separated by the polarization beam splitting element, for example, a polarization beam splitting prism (PBS) separates P polarized light and S-polarized light, when P-polarized light passes through the corresponding first polarization adjustment element, and then is reflected and passes through the first polarization adjustment element again, its polarization state becomes S polarization.
  • PBS polarization beam splitting prism
  • the first polarization adjustment element may be a (n*90+45) degree polarization rotator, such as a Faraday magneto-optical rotator, a liquid crystal polarization rotator, etc.; the first polarization adjustment element may also be (n/2+ 1/4) Lambda wave plate 4, where n can be any integer.
  • this application uses a common polarization beam splitting prism 3 (PBS) and a 1/4 ⁇ wave plate 4 in the solutions shown in FIGS. 6A-6C and FIGS. 9A-9C to illustrate the solution of the application. Mode of operation, but this does not mean that the solution of this application can only be realized by the combination of PBS and 1/4 ⁇ wave plate 4. It is only an optional implementation of this application; the above-listed and any other can realize polarization splitting Both the components and the components capable of changing the polarization state can be combined and applied to achieve the purpose of the present application.
  • This application exemplifies an embodiment in which a birefringent crystal is used instead of the PBS in FIG. 11.
  • the laser light emitted by the laser light source is collimated by the first lens 2 and then directed to the PBS.
  • the laser light after passing through the PBS becomes a single polarization, such as P-polarized light, and then passes through 1 for the first time.
  • /4 ⁇ wave plate 4 and directed to the FP optical cavity.
  • the directly reflected light generated by the first mirror 5 returns along the original optical path and is directed to the 1/4 ⁇ wave plate 4, and passes through the 1/4 ⁇ wave plate 4 for the second time.
  • the polarization of the laser The state will be converted to S polarization, and when it is directed to the PBS, it will be reflected by the PBS at 90 degrees and cannot pass through the PBS.
  • a second polarization adjustment element is placed inside a hollow FP optical cavity composed of a first reflector 5 and a second reflector 6 with high reflectivity.
  • the second polarization adjustment element may have any Polarization rotator with non-zero polarization rotation angle or glass slide made of birefringent crystal.
  • the F-P optical cavity itself is made of a material with birefringence effect coated with high reflection films on both sides.
  • a birefringent glass 7 ie, the second polarization adjusting element
  • the light coupled into the F-P optical cavity usually does not change its polarization direction.
  • the present application installs piezoelectric ceramic 9 on the mirror of the FP optical cavity, thereby allowing the cavity length of the FP optical cavity to be adjusted, and the change of the FP optical cavity length will cause the distribution of its longitudinal mode Change, and finally make the laser lock to a different frequency, to achieve high-speed modulation of the laser frequency.
  • a phase shifter 8 is arranged at any position between the semiconductor laser 1 and the F-P optical cavity to adjust the round-trip phase of the laser to optimize the effect of self-locking frequency.
  • the phase shifter 8 can be, for example, an optical crystal.
  • the refractive index of the optical crystal can be changed by changing the temperature, pressure, or voltage to modulate the phase of the laser, or it can be changed by changing the length of the physical path traveled by the light. Phase.
  • the birefringent glass 7 is arranged downstream of the FP optical cavity 11, and at the same time, another cavity is arranged downstream of the birefringent glass 7
  • the reflector 10, for example, a second lens 14 may be arranged between the FP optical cavity 11 and the external reflector 10 to collimate the transmitted light (as shown in FIG. 6B); or the transmitted light Converging on the external cavity mirror 10 (as shown in FIG. 6C), wherein, when the second lens 14 is configured to condense the transmitted light, the external cavity mirror 10 can be allowed to have a larger angle
  • the adjustment range does not need to be strictly perpendicular to the transmitted light, thereby making the assembly and adjustment of the external mirror 10 more convenient.
  • FIG. 2 please refer to the background art shown in FIG. 2.
  • the birefringent glass 7 Since the birefringent glass 7 is arranged outside the FP optical cavity 11, only the light that passes through the FP optical cavity 11 and is directed to the external mirror 10 and reflected by the external mirror 10 will pass through the birefringent glass. Plate 7, while the light oscillates in the FP optical cavity 11, the polarization state will not change. Therefore, although there is still an uncontrollable small difference in the Q value of the FP optical cavity 11, since the number of times the light passes through the birefringent glass plate 7 is two round trips, it is finally emitted to the 1/4 ⁇ wave plate 4 and the PBS The ratio of S-polarized light to P-polarized light in the feedback light becomes controllable.
  • such an arrangement also allows adjustment of the polarization state composition of the final feedback light by adjusting the second polarization adjustment element (for example, adjusting the thickness and angle of the birefringent glass 7).
  • the above-mentioned phase shifter 8 can also be arranged at any position between the semiconductor laser 1 and the external mirror 10.
  • the above-mentioned phase shifter 8 is arranged between the semiconductor laser 1 and the F-P optical cavity 11.
  • the phase shifter 8 can also be arranged at any position between the F-P optical cavity 11 and the external mirror 10.
  • the solutions described in the foregoing are mainly aimed at linewidth suppression and frequency modulation performed by semiconductor lasers, but the laser is not limited to semiconductor lasers, and can be other types such as solid-state lasers, fiber lasers, etc.
  • the semiconductor laser mentioned here refers to a laser with a resonant cavity that uses a semiconductor crystal material as a working medium. This type of laser has a relatively narrow line width. Generally, the line width is smaller than the interval between two adjacent longitudinal modes (Free Spectrum Range, FSR) of the FP optical cavity 11, therefore, as described in Figure 7 According to the principle of frequency locking, the final frequency of the laser is usually locked to the longitudinal mode of the FP cavity 11 closest to the frequency of the laser.
  • FSR Free Spectrum Range
  • the modulation of the laser frequency is achieved by, for example, adjusting parameters such as the cavity length and temperature of the F-P optical cavity 11, and then changing the longitudinal mode distribution of the F-P optical cavity 11.
  • the frequency of the semiconductor laser itself is basically fixed, the laser frequency obtained by the final modulation is usually only within a limited range around its own frequency. That is, the frequency modulation range of the above scheme is limited.
  • a semiconductor gain chip (hereinafter referred to as the gain chip 12) is used to replace the semiconductor laser 1 in the previous solution, while controlling the cavity length of the FP optical cavity 11 so that only one longitudinal mode is completely within the gain curve of the gain chip 12, for example Use a short cavity long FP optical cavity of a few microns.
  • the frequency of the laser will eventually be locked to the frequency of the longitudinal mode 1, which is completely inside the gain curve.
  • the piezoelectric ceramic 9 is used to adjust the cavity length of the FP optical cavity 11, so that the longitudinal mode 1 can be moved, and the alignment can be achieved in a large range (a few to tens of nanometers) close to the width of the gain curve.
  • the laser frequency is continuously modulated.
  • the piezoelectric ceramic 9 can also be used to adjust the position of the external mirror 10.
  • the scheme shown in Figure 8 allows continuous modulation of the laser frequency in a larger range, but this needs to be based on a premise that the cavity length of the FP optical cavity 11 should be less than the preset value, so that multiple longitudinal modes It is satisfied that only one is completely inside the gain curve. If the cavity length of the F-P optical cavity 11 cannot meet this condition, and two or more longitudinal modes appear in the gain curve at the same time, it will cause the final laser to appear at multiple frequencies at the same time.
  • an F-P optical cavity with a short cavity length has a lower Q value but a larger FSR; while an F-P cavity with a long cavity length can have a high Q value, but the FSR is smaller.
  • this application proposes an improved solution to the solution described in FIG. 8.
  • a bandpass filter with a low quality factor is set anywhere between the gain chip 12 and the FP optical cavity 11.
  • the bandpass filter may be an FP optical cavity, an interference filter, or a reflective grating , Or volume grating, or acousto-optic modulation filter, etc., and the band pass curve of the band pass filter can be adjusted and moved within the gain curve range of the gain chip 12.
  • the bandpass curve of the bandpass filter has a single bandpass peak, and the width of the bandpass curve of the single bandpass peak and the longitudinal mode spacing FSR of the FP cavity 11 satisfy one of the following conditions: there is only one at a time The longitudinal mode of the FP optical cavity is completely inside the band pass curve; or the band pass filter has a periodic band pass curve with a different FSR from the FP cavity 11, and the band pass filter has only one longitudinal mode frequency and FP at the same time The frequency of one longitudinal mode of the optical cavity 11 is aligned.
  • the band pass filter adopts the interference filter 13.
  • the width of the bandpass curve of the interference filter 13 shown should be smaller than the width of the gain curve.
  • the interference filter 13 should be matched with the FSR of the FP optical cavity 11, so that only one longitudinal mode is completely in the interference filter 13 Inside the bandpass curve.
  • the multiple longitudinal modes of the high-Q FP optical cavity 11 may all be located inside the gain curve, as shown in FIG. 10, since only the longitudinal modes that are also located inside the bandpass curve of the interference filter 13 correspond to Only the frequency of light can pass through the interference filter 13 and be fed back to the gain chip 12. Therefore, the final laser is a single-frequency laser whose laser frequency corresponds to the longitudinal mode completely located inside the bandpass curve of the interference filter 13 Frequency of.
  • the laser frequency can be adjusted by two methods.
  • One is the same as the previous one.
  • the piezoelectric ceramic 9 is used to adjust the cavity length of the FP optical cavity 11 to move the longitudinal mode within the bandpass curve of the interference filter 13. , And then change the frequency of the laser that is finally locked; the other is to rotate the interference filter 13 to make the band pass curve move within the gain curve and cover different longitudinal modes.
  • the above-mentioned two methods can be carried out in cooperation to realize the connection frequency modulation within the range close to the width of the gain curve.
  • Figure 12 shows a schematic diagram of the combined mode selection and frequency modulation of the bandpass filter with periodic bandpass curve and the longitudinal mode of the FP optical cavity.
  • the period is different from that of the high-Q FP optical cavity 11.
  • the frequency of the bandpass curve makes the FP optical cavity 11 and the bandpass filter each have and only one longitudinal mold has the same frequency at the same time, so that the laser lases at the single frequency.
  • By slightly moving the bandpass curve of the bandpass filter different longitudinal modes of the F-P optical cavity 11 can be selected to generate lasing. This method is also often referred to as the vernier effect.
  • the present application has at least the following advantages: the laser of the present application directly uses a Fabry Perot cavity with a higher quality factor as an external cavity optical feedback element, and at the same time, by adjusting the laser polarization state, it can Deal with the mode competition in optical feedback, so that the laser based on FP optical cavity 11 for optical feedback has a stable ultra-narrowband laser output; in addition, this application uses the cooperation of piezoelectric ceramic 9, gain chip 12, interference filter 13, etc. It realizes a large range of high-speed modulation of laser frequency while outputting ultra-narrowband laser.
  • an external cavity laser based on an FP optical cavity includes a semiconductor laser 1, a first lens 2 and an FP optical cavity.
  • the FP optical cavity shown is composed of a first mirror 5 and a second mirror which are sequentially arranged on the optical path.
  • Two mirrors 6 are formed; on the optical path between the first lens 2 and the first mirror 5 of the FP optical cavity, there is also a polarization splitter along the laser emitting direction (referring to the direction from the laser to the FP optical cavity).
  • the position and angle relative to the first mirror 5 and the second mirror 6 can be changed.
  • the second reflector 6 of the FP optical cavity is also provided with piezoelectric ceramic 9 for adjusting the length of the FP optical cavity; in the FP composed of the semiconductor laser 1 and the first reflector 5 and the second reflector 6
  • a phase shifter 8 is also arranged at any position between the optical cavities 11.
  • the phase shifter 8 is arranged between the first lens 2 and the polarization beam splitting prism 3.
  • the phase shifter 8 is an optical crystal that can change the refractive index by adjusting parameters such as temperature, pressure, or voltage to adjust the laser phase.
  • the birefringent glass sheet 7 may not be provided between the first mirror 5 and the second mirror 6.
  • the first mirror 5 and the second mirror 6 may be made of materials with birefringence. It is manufactured, and the first reflecting mirror 5 and the second reflecting mirror 6 are both plated with a reflecting film with higher reflectivity, which can also achieve the above-mentioned effect.
  • the difference from Embodiment 1 is that the birefringent glass 7 is arranged downstream of the FP optical cavity 11 (along the laser emission direction described in Embodiment 1), and at the same time, the double Downstream of the refractive glass 7 is also provided with an external mirror 10, the piezoelectric ceramic 9 is set on the mirror of the FP optical cavity 11 or the external mirror 10 (in this embodiment, the piezoelectric ceramic 9 is set On the external reflector 10); in addition, a second lens 14 is also provided on the optical path between the birefringent glass 7 and the FP optical cavity 11 to collimate the laser light emitted from the FP optical cavity 11 to be vertical It is directed to the mirror 10 outside the cavity.
  • the difference from Embodiment 2 is that the birefringent glass 7 is arranged between the F-P optical cavity 11 and the second lens 14, and the second lens 14 condenses the transmitted light on the external mirror 10.
  • Embodiment 1-3 The difference from Embodiment 1-3 is that the semiconductor laser 1 is replaced by the gain chip 12. At the same time, an F-P optical cavity with a shorter cavity length is used, so that only one of the multiple optical cavity longitudinal modes of the F-P optical cavity can be completely inside the gain curve of the gain chip 12 at the same time.
  • the difference from Embodiment 4 is that the FP optical cavity 11 with a high Q value is used for optical feedback, and the gain chip 12 and the FP optical cavity 11
  • An interference filter 13 is arranged at any position of the (in this embodiment, the interference filter 13 is arranged between the 1/4 ⁇ wave plate 4 and the FP optical cavity 11), and the angle of the interference filter 13 is adjustable, and at least By adjusting the angle of the interference filter 13, the band-pass curve of the interference filter 13 can be moved within the range of the gain curve of the gain chip 12; in addition, the width of the band-pass curve and the high Q value FP
  • the longitudinal mode spacing FSR of the optical cavity 11 satisfies the following conditions: at the same time, only one longitudinal mode can be completely inside the bandpass curve.
  • the interference filter 13 can be arranged at any position between the gain chip 12 and the external mirror 10, for example, between the FP optical cavity 11 and the external mirror 10. position.
  • a birefringent crystal 15 is used instead of the polarization beam splitting prism 3 in Embodiments 1-5.
  • the laser light source emits p (or s) polarized light, which passes through the birefringent crystal 15 and the 1/4 ⁇ wave plate 4. After the light directly reflected by the first mirror 5 of the FP optical cavity 11 passes through the 1/4 ⁇ wave plate 4 for the second time, the polarization direction is rotated to the s (or p) polarization state, and the edge of the birefringent crystal 15 is different from that of the incident light.
  • the path is separated and cannot enter the laser, so as to avoid the interference of the light directly reflected by the first mirror 5 of the FP optical cavity 11 on the injection feedback of the laser.

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Abstract

一种基于法布里波罗F-P光腔的外腔激光器，包括沿激光射出方向依次设置的激光光源、第一透镜（2）、F-P光腔（11）；其中，F-P光腔（11）由第一反射镜（5）和第二反射镜（6）构成；激光光源与F-P光腔（11）之间的光路上还沿激光射出方向依次设有偏振分光元件和第一偏振调整元件；偏振分光元件仅允许特定偏振态的光透过而分离其他正交偏振态的光；第一偏振调整元件能将往返两次透过第一偏振调整元件的光的偏振态改变为另一正交的偏振态，F-P光腔（11）的内部还设有第二偏振调整元件，或者第一反射镜（5）和第二反射镜（6）由具有双折射效应的材料镀高反射膜构成。

Description

基于法布里波罗光腔的外腔激光器
本申请要求申请日为2019年7月23日、申请号为201910663853.6的中国专利申请的优先权，该申请的全部内容通过引用结合在本申请中。
技术领域
本申请涉及激光领域，例如涉及一种基于法布里波罗光腔的外腔激光器。
背景技术
激光器的相位噪声或者线宽和激光谐振腔的品质因子(下称Q值)直接相关。半导体激光器通常以工作介质，即半导体晶体的解理面为谐振腔，而受限于材料特性和晶体成型工艺，其Q值通常较低。
相关技术中，降低激光器的相位噪声或者线宽的主流方案有两类。第一类是使用外腔反馈元件进行光反馈，增加轴向光的反射率，使得激光器与外腔反馈元件组成的复合光腔的整体Q值获得提高。图1-图2描述了这类外腔反馈方案的两种典型方式(Optics Letters/Vol.13,No.10/October 1988page 826)，图1中使用的外腔反馈元件为光栅，所述光栅可以旋转，进而可实现选择性的反馈特定波长的光返回激光器；图2中使用的外腔反馈元件为反射镜，并且其展示了在激光器与反射镜之间设置一个干涉滤波片，通过干涉滤波片的旋转可以实现对多个纵模的单一选择。这类方案本质上都是通过加长光腔和反射率提高复合光腔Q值进而降低激光噪声，并配合光栅或滤波片实现对单一纵模的选择和切换。
围绕上述方案衍生出了许多改进形式，示例性的，如图3所示(IEEE PHOTONICS TECHNOLOGY LETTERS,VOL.24,NO.18,SEPTEMBER 15,2012)。其展示了基于两个干涉滤波片选择性产生单频激光的方案。
这类方案能够实现激光线宽从几个kHz到几百kHz的激光器，但是很难突破KHz及以下，其原因是光栅或单一反射镜构成的复合光腔Q值仍然较低。另外，干涉滤波片的Q值也很低。
虽然使用极窄的滤波器，如美国专利US8605760A1中所描述的，使用线宽在MHz左右的超高Q值的回音壁光腔作为滤波构建复合光腔，可以实现线宽在百Hz甚至Hz级别的激光。但这类超高Q值的回音壁光腔内的光强极大，受材料的非线性效应，热效应的限制，该类方案产生的激光能量和频率稳定性均受到很大限 制，且其制作工艺极其复杂昂贵，难以实现工业化应用。
第二类方案是使用电的负反馈方法压制激光频率噪声，图4展示了这类方法的典型方式(Am.J.Phys.,Vol.69,No.1,January 2001)。这类方法通常被称为Pound-Drever-Hall(PDH)方法，其首先需要采用具有超高Q值的光腔对激光的频率噪声进行测量。法布里波罗光腔(FabryPerot，下称F-P光腔)是目前多种光腔中Q值和稳定性最好的，研究的历史最久，常用来作为PDH方法的光腔。使用这类方案，世界上很多科研小组实现了Hz以下的超低噪声和超稳定的激光器。但是采用该类方案的激光器系统极其复杂，并且电路反馈的带宽有限，通常最高仅至MHz，无法对高频的激光频率噪声进行压制。因此，该类方案目前还仅局限在实验室使用。
相关技术中也有直接使用F-P光腔进行光反馈以压低激光线宽的尝试，图5为示例性的使用F-P光腔进行光反馈的实施方案。这样的设计能够使整个系统大大简化，同时也避免了电反馈无法对高频激光噪声有效压制的缺陷。但由于F-P光腔的镜面反射率极高，其共振模式在镜面处总是垂直于镜面，激光要高效的耦合进入光腔，必须垂直于镜面入射。这种模式下在F-P光腔处，存在来自反射镜1的直接反射及来自光腔的两种光反馈，而这两种反馈之间的模式竞争会严重影响激光器的稳定性。
发明内容
本申请提供了一种基于法布里波罗F-P光腔的外腔激光器。本申请的激光器直接使用F-P光腔进行光反馈，能够处理第一面反射镜的反射光与F-P光腔的反馈光之间的模式竞争的情况，同时还能够实现在较大范围内对激光频率的高速连续调制。
一实施例提供一种基于法布里波罗F-P光腔的外腔激光器，包括沿激光射出方向依次设置的激光光源、第一透镜、F-P光腔；其中，所述F-P光腔由第一反射镜和第二反射镜构成；
所述激光光源与所述F-P光腔之间的光路上还沿激光射出方向依次设有一个偏振分光元件和一个第一偏振调整元件；所述偏振分光元件仅允许特定偏振态的光透过而分离其他正交偏振态的光；所述第一偏振调整元件能将往返两次透过所述第一偏振调整元件的光的偏振态改变为另一正交的偏振态，所述F-P光腔的内部还设有一个第二偏振调整元件，或者所述第一反射镜和所述第二反射 镜由具有双折射效应的材料镀高反射膜构成。
一实施例提供一种基于法布里波罗F-P光腔的外腔激光器，包括沿激光射出方向依次设置的激光光源、第一透镜、F-P光腔；其中，所述F-P光腔由第一反射镜和第二反射镜构成；
所述激光光源与所述F-P光腔之间的光路上还沿激光射出方向依次设有一个偏振分光元件和一个第一偏振调整元件；所述偏振分光元件仅允许特定偏振态的光透过而分离其他正交偏振态的光；所述第一偏振调整元件能将往返两次透过所述第一偏振调整元件的光的偏振态改变为另一正交的偏振态；
所述F-P光腔下游设有第二偏振调整元件，同时所述第二偏振调整元件的下游还设有一个腔外反射镜。
附图说明
图1为相关技术中使用光栅进行光反馈的示意图；
图2为相关技术中使用反射镜进行光反馈的示意图；
图3为相关技术中基于两个干涉滤波片选择性产生单频激光的示意图；
图4为相关技术中使用电的负反馈方法压制激光频率噪声的示意图；
图5为相关技术中直接使用F-P光腔进行光反馈产生模式竞争的示意图；
图6A为本申请提供的处理F-P光腔直接光反馈模式竞争的示意图；
图6B为对图6A所示方案的第一种改进示意图；
图6C为对图6A所示方案的第二种改进示意图；
图7为F-P光腔对半导体激光器的锁频原理示意图；
图8为半导体增益芯片的增益曲线与F-P光腔纵模谱线示意图；
图9A为使用增益芯片和高Q值F-P光腔实现超窄带激光和大范围连续调频的示意图；
图9B为对图9A所示方案的第一种改进示意图；
图9C为对图9A所示方案的第二种改进示意图；
图10为增益曲线与F-P光腔的纵模、干涉滤波片的带通曲线的复合频谱示意图；
图11为使用双折射晶体替代偏振分光棱镜实现偏振分光的示意图；
图12为具有周期性带通曲线的带通滤波器与F-P光腔纵模复合选模和调频的示意图。
图中：1为半导体激光器，2为第一透镜，3为偏振分光棱镜，4为1/4λ波片，5为第一反射镜，6为第二反射镜，7为双折射玻片，8为相移器，9为压电陶瓷，10为腔外反射镜，11为F-P光腔，12为增益芯片，13为干涉滤波片，14为第二透镜，15为双折射晶体。
具体实施方式
如图6A-图6C所示，本申请所提供的方案中，使用具有较高Q值的F-P光腔11作为外腔或者外腔中的超窄带滤波器，利用其超精细的波长选择性反馈而实现压低激光器频率相位噪声。激光光源发出的激光经第一透镜2准直后垂直射向F-P光腔11，从而所述激光可以高效的耦合进入F-P光腔11，并在腔内多次反射后反馈回激光光源。而如上文背景技术中所描述的，仅仅依靠这样的布置方式无法处理前述的模式竞争。为此，本申请还进行了如下的设计。
在第一透镜2与F-P光腔11之间的光路上沿激光出射方向依次设置一个偏振分光元件和一个第一偏振调整元件。
所述偏振分光元件仅允许特定偏振态的光透过，而分离其他正交的偏振光；例如仅允许P偏振光透过而分离S偏振光或反之。所述的偏振分光元件可以是依赖于镀膜或微纳结构的偏振分光元件，例如偏振分光棱镜(Polarizing Beam Splitter，PBS)，45度偏振分光片，以及布鲁斯特(Brewster)角的偏振分光片等；所述的偏振分光元件也可以是依赖于双折射晶体效应的元件，例如Glan-Taylor偏振器、Glan-Tompson偏振器、沃拉斯顿偏振器，Rochon棱镜等。
所述第一偏振调整元件能将往返两次透过其的光的偏振态在上述偏振分光元件所分离的两个正交偏振态之间改变，例如偏振分光棱镜(PBS)分离P偏振光和S偏振光，当P偏振光透过所述对应的第一偏振调整元件，然后经反射并再次透过所述的第一偏振调整元件，其偏振态变为S偏振。所述的第一偏振调整元件可以是(n*90+45)度偏振旋转片例如法拉第磁光旋转片、液晶类偏振旋转器等；所述第一偏振调整元件也可以是(n/2+1/4)λ波片4,这里n可以是任意整数。
为便于理解，本申请在图6A-图6C及图9A-图9C所示出的方案中均使用常见的偏振分光棱镜3(PBS)和1/4λ波片4的组合以阐释本申请方案的运行方式，但这并不代表本申请的方案仅能依托于PBS和1/4λ波片4的组合来实现，只是本申请可选的实施方式；上文所列举的及其他任何能够实现偏振分光的元件及能够实现偏振态改变的元件均可被组合应用以实现本申请的目的。本申请在图11 中举例阐述了一种使用双折射晶体替代所述PBS的实施方式。
如图6A所示，由激光光源射出的激光在经第一透镜2准直后射向PBS，透过PBS后的激光成为具有单偏振态的，例如P偏振光，随后第一次透过1/4λ波片4并射向F-P光腔。在F-P光腔处，由第一反射镜5产生的直接反射光沿原光路返回并射向1/4λ波片4，并第二次透过1/4λ波片4，此时，激光的偏振态将转变为S偏振，再射向PBS时，将被PBS以90度反射出去而不能透过PBS。
示例性的，在由具有高反射率的第一反射镜5和第二反射镜6构成中空的F-P光腔的内部置入一个第二偏振调整元件，所述第二偏振调整元件可以是具有任意非零偏振旋转角度的偏振旋转片或者由双折射晶体构成的玻片。或者该F-P光腔本身由具有双折射效应的材料在两面镀高反膜而构成。为便于理解，本申请在图6A及图9A所示的实施方式中，在所述中空的F-P光腔内部设置了一个双折射玻片7(即第二偏振调整元件)。耦合进入F-P光腔的光，其偏振方向通常不会改变，若直接经多次反射后反馈射向半导体激光器1也会同样被PBS以90度角反射出去而不能透过。但由于在F-P光腔内置入了一个前述的任意非零偏振旋转角度的偏振旋转片或者由双折射晶体构成的玻片，光在F-P光腔内多次往返透过双折射玻片7的过程中，其偏振态已经发生了改变，处于S和P的混合偏振态。因此，经F-P光腔反馈的光再次通过第一偏振调整元件和PBS时，S偏振光将被PBS反射，但P偏振光则可以直接透射，并反馈回激光器。
已知的是，使用F-P光腔进行光反馈可以实现对激光器频率的锁定，其原理如图7所示，通常情况下，半导体激光器1自身均带有谐振腔，因此，其出射激光的线宽已经较小，而当半导体激光器1发出的激光本身的频率靠近F-P光腔的多个纵模频率中的一个时，经F-P光腔反馈后的激光的频率将被锁定在该纵模频率上。基于这样的锁频原理，本申请在F-P光腔的反射镜上设置压电陶瓷9，进而允许对F-P光腔的腔长进行调整，而F-P光腔腔长的变化将使得其纵模的分布改变，并最终使得激光被锁定到不同的频率上，实现对激光频率的高速调制。
由于外腔反馈自锁频的方法对于光在激光器和外腔之间往返的光程差也较敏感。因此，本申请在半导体激光1和F-P光腔之间的任意位置设置一个相移器8，对激光的往返相位进行调节，优化自锁频的效果。所述的相移器8可以是例如光学晶体，通过改变温度、压力，或者加电压以改变所述光学晶体的折射率以调制激光的相位，也可以通过改变光所走过的物理路径长度改变相位。
以上提供的方案可以较好的处理模式竞争的情况，实现对例如半导体激光 器1激光频率的压缩和高速调制。
但是，即使是相同厂家使用同一工艺生产的同一批次相同型号的光腔产品，两个不同的光腔之间总是会存在一些微小的差异。这使得，在例如两套采用上述方案的激光器中，光在各自F-P光腔中实际往返的次数并不完全相同，也即光往返透过双折射玻片7的次数不完全相同，这导致了通过上述方案中的F-P光腔反馈射向PBS的光中的S偏振光与P偏振光的比例存在差异，因此，实际反馈回到激光光源的激光的光能量不同。此外，两套激光器在制造过程中，其双折射玻片7在F-P光腔内的具体位置和方向也无法做到完全相同。这两个因素均会导致实际生产制造的激光器的性能存在微小偏差，产品性能的重复性难以保证。
在一实施例中，如图6B、图6C所示，将所述的双折射玻片7设在F-P光腔11的下游，并同时在所述双折射玻片7的下游再设置一个腔外反射镜10，示例性的，还可以在所述F-P光腔11与所述腔外反射镜10之间设置一个第二透镜14以准直透射光(如图6B所示)；或者将透射光汇聚于腔外反射镜10(如图6C所示)，其中，当所述第二透镜14被设置为汇聚所述透射光时，所述的腔外反射镜10可以被允许具有更大的角度调整范围，而无需严格的垂直于透射光，进而使得所述腔外反射镜10的组装和调节更为方便，这一点可参照图2中所展示的背景技术。
由于双折射玻片7被设置在了F-P光腔11的外部，只有透过F-P光腔11射向腔外反射镜10及被腔外反射镜10反射的光才会穿过所述双折射玻片7，而光在F-P光腔11内振荡的过程中，则不会产生偏振态的变化。因此，尽管F-P光腔11的Q值仍然存在不可控的微小差异，但由于光透过所述双折射玻片7的次数均为往返两次，所以最终射向1/4λ波片4和PBS的反馈光中的S偏振光与P偏振光的比例变得可控。
可选的，这样的设置还允许通过调整所述的第二偏振调整元件(例如调整双折射玻片7的厚度和角度)对最终反馈光的偏振态组成进行调整。
在一实施例中，上述相移器8还可以设置在在半导体激光器1和腔外反射镜10之间的任意位置上。上述相移器8设置在半导体激光器1和F-P光腔11之间，可选的，相移器8还可以位于设置在F-P光腔11和腔外反射镜10之间的任意位置。
前文中所描述的方案主要针对的是半导体激光器进行的线宽压制和调频，但该激光器不局限于半导体激光，可以是其他类型的例如固体激光器，光纤激光器等。此处所述的半导体激光器指的是自身带有谐振腔的以半导体晶体材料为工作介质的激光器。这类激光器其自身就具有较窄的线宽，一般情况下，其 线宽均小于F-P光腔11相邻两个纵模的间隔(Free Spectrum Range，FSR)，因此，如图7中所描述的锁频原理，激光最后的频率通常被锁定在最靠近激光器自身频率的F-P光腔11的纵模上。对于激光频率的调制依靠例如对F-P光腔11的腔长、温度等参数的调整，进而改变F-P光腔11的纵模分布来实现。但是，由于半导体激光器本身的频率基本固定，因此，最终调制获得的激光频率通常仅在其自身频率周围的有限范围内。即，上述方案的频率调制范围有限。
为了使本申请的方案具备在更大范围内进行调频的功能。本申请对前文描述的方案进行了改进。
示例性的，使用半导体增益芯片(下称增益芯片12)替换前文方案中的半导体激光器1，同时控制F-P光腔11的腔长，使得只有一个纵模完全处于增益芯片12的增益曲线内，例如使用几个微米的短腔长F-P光腔。这样，如图8中所示，激光的频率最终将被锁定到完全处于增益曲线内部的纵模1的频率上。在这样前提下，再使用压电陶瓷9调整F-P光腔11的腔长，可以使纵模1移动，进而可以实现在接近增益曲线宽度的较大范围内(几个至几十个纳米)对激光频率进行连续的调制。
在一实施例中，还可以利用压电陶瓷9调整腔外反射镜10的位置。
可以看到，图8所展示的方案允许在较大的范围内对激光频率进行连续调制，不过这需要基于一个前提，即F-P光腔11的腔长应当小于预设值，使得多个纵模满足只有一个完全处于增益曲线内部。如果，F-P光腔11的腔长不能满足这一条件，而使得在增益曲线内同时出现两个或更多个纵模时，则会导致最终的激光同时出现多个频率。
已知的是，F-P光腔11的腔长与其性能之间存在预设的对应关系。通常短腔长的F-P光腔，其Q值较低，但FSR较大；而长腔长的F-P光腔，其Q值可以做的很高，但FSR较小。而在很多情况下，期望光腔具有高的Q值，以使经光腔进行光反馈后得到的激光具有较窄的线宽。
为实现基于超高Q值的F-P光腔11的超窄带激光器，同时允许进行大范围的调频，本申请提出一种针对图8所描述的方案的改进方案。
示例性的，在增益芯片12与F-P光腔11之间的任意位置再设置一个低品质因子的带通滤波器，所述带通滤波器可以是F-P光腔，干涉滤波片，或反射型光栅，或体光栅，或声光调制滤波器等，且带通滤波器的带通曲线可以在增益芯片12的增益曲线范围内调节移动。此外，带通滤波器的带通曲线具有单一的带通峰， 单一带通峰的带通曲线的宽度与F-P光腔11的纵模间距FSR之间满足如下条件之一：同一时刻仅有一个F-P光腔的纵模完全处于带通曲线的内部；或者带通滤波器具有与F-P光腔11不同FSR的周期性的带通曲线,且同一时刻带通滤波器仅有一个纵模频率与F-P光腔11的一个纵模频率对齐。示例性的，如图9A-图9C所示，带通滤波器采用的是干涉滤波片13。所示干涉滤波片13的带通曲线宽度应当小于增益曲线的宽度，同时，该干涉滤波片13应当与F-P光腔11的FSR相配合，以使得仅有一个纵模完全处于干涉滤波片13的带通曲线内部。
这样虽然高Q值的F-P光腔11的多个纵模可能都位于增益曲线的内部，但是如图10所示，由于仅有同时位于干涉滤波片13的带通曲线内部的纵模所对应的频率的光才可以透过所述干涉滤波片13反馈会到增益芯片12，因此，最终得到的激光为单频激光，其激光频率为完全位于干涉滤波片13带通曲线内部的纵模所对应的频率。
此时，对激光频率的调整可以通过两种手段进行，一种是与前文相同，通过压电陶瓷9调整F-P光腔11的腔长，使纵模在干涉滤波片13的带通曲线内移动，进而改变最终被锁定的激光的频率；另一种则是通过旋转所述干涉滤波片13，使其带通曲线在增益曲线内移动，并覆盖不同的纵模。可选的，上述的两种手段可以配合进行，以实现在接近增益曲线宽度的范围内的连线调频。
图12所示的为具有周期性带通曲线的带通滤波器与F-P光腔纵模复合选模和调频的示意图，其周期与高Q值F-P光腔11的不同，通过调节带通滤波器的带通曲线频率，在同一时刻使得F-P光腔11和带通滤波器各自有且仅有一个纵模具有相同的频率，使得激光在该单一频率产生激射。通过微小的移动带通滤波器的带通曲线，可以选择F-P光腔11的不同的纵模产生激射，该方法也常被称为游标效应。
相比于相关技术，本申请至少具备如下优点：本申请的激光器直接使用具有较高品质因子的法布里波罗光腔作为外腔光反馈元件，同时，通过对激光偏振态的调整，能够处理光反馈时的模式竞争情况，使基于F-P光腔11进行光反馈的激光器具有稳定的超窄带激光输出；此外，本申请通过压电陶瓷9、增益芯片12、干涉滤波片13等的配合，实现了在输出超窄带激光的同时对激光频率的大范围高速调制。
实施例1
如图6A所示，一种基于F-P光腔的外腔激光器，包括半导体激光器1，第一透镜2和F-P光腔，所示F-P光腔由依次设置在光路上的第一反射镜5和第二反射镜6构成；在所述第一透镜2与F-P光腔的第一反射镜5之间的光路上还沿激光射出方向(指从激光器射向F-P光腔的方向)依次设有偏振分光棱镜3和1/4λ波片4；同时，所述F-P光腔的内部，位于第一反射镜5和第二反射镜6之间还设置有一双折射玻片7，所述双折射玻片7相对于第一反射镜5和第二反射镜6的位置和角度均可以改变。所述F-P光腔的第二反射镜6上还设有调节F-P光腔腔长的压电陶瓷9；在所述半导体激光器1与所述第一反射镜5和第二反射镜6组成的F-P光腔11之间的任意位置处还设置有一个相移器8，本实施例中将相移器8设置在在第一透镜2和偏振分光棱镜3之间。所述相移器8为可以通过调节诸如温度、压力或电压等参数进而改变折射率以调节激光相位的光学晶体。
在一实施例中，还可以不在第一反射镜5和第二反射镜6之间设置双折射玻片7，此时第一反射镜5和第二反射镜6可以由具有双折射效应的材料制成，且在第一反射镜5和第二反射镜6上均镀上具有较高反射率的反射膜，同样可以实现上述效果。
实施例2
如图6B所示，不同于实施例1的是，所述双折射玻片7被设置在F-P光腔11的外部下游(沿实施例1中所述的激光射出方向)，同时，所述双折射玻片7的下游还设有一腔外反射镜10，所述的压电陶瓷9被设在F-P光腔11的反射镜上或腔外反射镜10上(本实施例中压电陶瓷9设置在外反射镜10上)；此外，在所述双折射玻片7和F-P光腔11之间的光路上还设有一个第二透镜14，用以将F-P光腔11射出的激光准直后垂直射向腔外反射镜10。
实施例3
如图6C所示，不同于实施例2的是，双折射玻片7设置于F-P光腔11和第二透镜14之间，第二透镜14将透射光汇聚于腔外反射镜10。
实施例4
不同于实施例1-3的是，使用增益芯片12替换半导体激光器1。同时，使用具有较短腔长的F-P光腔，以使F-P光腔的多个光腔纵模中同时仅能有一个完全 处于所述增益芯片12的增益曲线内部。
实施例5
如图9A-图9C及图10所示，不同于实施例4的是，使用具有高Q值的F-P光腔11进行光反馈，并在所述增益芯片12与所述F-P光腔11之间的任意位置上设一个干涉滤波片13(本实施例中，干涉滤波片13设置在1/4λ波片4和F-P光腔11之间)，所述干涉滤波片13的角度可调，且至少通过调整所述干涉滤波片13的角度，可使干涉滤波片13的带通曲线在所述增益芯片12的增益曲线范围内移动；另外，所述带通曲线的宽度与所述高Q值F-P光腔11的纵模间距FSR之间满足如下条件：同时仅能有一个纵模完全处于带通曲线的内部。
在一实施例中，干涉滤波片13可以设置在所述增益芯片12与所述腔外反射镜10之间的任意位置上，例如设置在F-P光腔11与腔外反射镜10之间的任意位置。
实施例6
如图11所示，使用双折射晶体15替代实施例1-5中的偏振分光棱镜3。激光光源发射p(或s)偏振光，经过双折射晶体15和1/4λ波片4。由F-P光腔11的第一反射镜5直接反射的光第二次经过1/4λ波片4后，偏振方向旋转为s(或p)偏振态，在双折射晶体15中沿与入射光不同的路径分开，无法进入激光器，从而避免F-P光腔11的第一反射镜5直接反射的光对激光的注入反馈干扰。

Claims (22)

  1. 一种基于法布里波罗F-P光腔的外腔激光器，包括沿激光射出方向依次设置的激光光源、第一透镜、F-P光腔；其中，所述F-P光腔由第一反射镜和第二反射镜构成；
    所述激光光源与所述F-P光腔之间的光路上还沿激光射出方向依次设有一个偏振分光元件和一个第一偏振调整元件；所述偏振分光元件仅允许特定偏振态的光透过而分离其他正交偏振态的光；所述第一偏振调整元件能将往返两次透过所述第一偏振调整元件的光的偏振态改变为另一正交的偏振态，所述F-P光腔的内部还设有一个第二偏振调整元件，或者所述第一反射镜和所述第二反射镜由具有双折射效应的材料镀高反射膜构成。
  2. 如权利要求1所述的基于法布里波罗F-P光腔的外腔激光器，还包括腔外反射镜，且沿激光射出方向，所述腔外反射镜设置于所述F-P光腔的下游。
  3. 如权利要求1或2所述的基于法布里波罗F-P光腔的外腔激光器，其中：所述偏振分光元件为使用镀膜或微纳结构的偏振分光棱镜，或布鲁斯特偏振器，或具有晶体双折射效应的偏振分光元件；所述第一偏振调整元件为(n*90+45)度法拉第旋光片或(n*90+45)度液晶偏振旋转片或(n/2+1/4)λ波片，其中，n为任意整数。
  4. 如权利要求1或2所述的基于法布里波罗F-P光腔的外腔激光器，还包括压电陶瓷，所述压电陶瓷设置于所述第二反射镜上，且所述压电陶瓷设置为调节所述F-P光腔的腔长。
  5. 如权利要求2所述的基于法布里波罗F-P光腔的外腔激光器，还包括压电陶瓷，所述压电陶瓷设置于所述腔外反射镜上，且所述压电陶瓷设置为调节所述腔外反射镜的位置。
  6. 如权利要求1-5中任一项所述的基于法布里波罗F-P光腔的外腔激光器，其中：所述激光光源为增益芯片。
  7. 如权利要求6所述的基于法布里波罗F-P光腔的外腔激光器，其中：所述激光光源与所述F-P光腔之间设有带通滤波器；且所述F-P光腔为具有高Q值的光腔。
  8. 如权利要求2或5所述的基于法布里波罗F-P光腔的外腔激光器，其中：所述激光光源为增益芯片，且所述激光光源与所述腔外反射镜之间设有带通滤波器；且所述F-P光腔为具有高Q值的光腔。
  9. 如权利要求7或8所述的基于法布里波罗F-P光腔的外腔激光器，其中： 所述带通滤波器具有单一带通峰的，或周期性的带通曲线，且所述带通曲线可以在所述增益芯片的增益曲线范围内调节移动。
  10. 如权利要求9所述的基于法布里波罗F-P光腔的外腔激光器，其中：所述带通滤波器具有单一带通峰的带通曲线，所述带通滤波器的单一带通峰的带通曲线的宽度与所述F-P光腔的纵模间距FSR之间满足：同一时刻仅有一个所述F-P光腔的纵模完全处于所述带通曲线的内部。
  11. 如权利要求9所述的基于法布里波罗F-P光腔的外腔激光器，其中：所述带通滤波器具有周期性的带通曲线，所述带通滤波器的周期性的带通曲线具有与所述F-P光腔不同的FSR,且同一时刻所述带通滤波器仅有一个纵模频率与所述F-P光腔的一个纵模频率对齐。
  12. 如权利要求1-8中任一项所述的基于法布里波罗F-P光腔的外腔激光器，还包括相移器，所述相移器设置于所述激光光源与所述F-P光腔之间。
  13. 如权利要求8所述的基于法布里波罗F-P光腔的外腔激光器，还包括相移器，所述相移器设置于所述激光光源与所述腔外反射镜之间。
  14. 一种基于法布里波罗F-P光腔的外腔激光器，包括沿激光射出方向依次设置的激光光源、第一透镜、F-P光腔；其中，所述F-P光腔由第一反射镜和第二反射镜构成；
    所述激光光源与所述F-P光腔之间的光路上还沿激光射出方向依次设有一个偏振分光元件和一个第一偏振调整元件；所述偏振分光元件仅允许特定偏振态的光透过而分离其他正交偏振态的光；所述第一偏振调整元件能将往返两次透过所述第一偏振调整元件的光的偏振态改变为另一正交的偏振态；
    所述F-P光腔的下游设有第二偏振调整元件，同时所述第二偏振调整元件的下游还设有一个腔外反射镜。
  15. 如权利要求14所述的基于法布里波罗F-P光腔的外腔激光器，其中：所述偏振分光元件为使用镀膜或微纳结构的偏振分光棱镜，或布鲁斯特偏振器，或具有晶体双折射效应的偏振分光元件；所述第一偏振调整元件为(n*90+45)度法拉第旋光片或(n*90+45)度液晶偏振旋转片或(n/2+1/4)λ波片，其中，n为任意整数。
  16. 如权利要求14或15所述的基于法布里波罗F-P光腔的外腔激光器，还包括压电陶瓷，所述压电陶瓷设置于所述第二反射镜上或所述腔外反射镜上，且所述压电陶瓷设置为调节所述F-P光腔的腔长或所述腔外反射镜的位置。
  17. 如权利要求14-16中任一项所述的基于法布里波罗F-P光腔的外腔激光器，其中：所述激光光源为增益芯片。
  18. 如权利要求17所述的基于法布里波罗F-P光腔的外腔激光器，其中：所述激光光源与所述F-P光腔之间，或所述激光光源与所述腔外反射镜之间设有带通滤波器；且所述F-P光腔为具有高Q值的光腔。
  19. 如权利要求18所述的基于法布里波罗F-P光腔的外腔激光器，其中：所述带通滤波器具有单一带通峰的，或周期性的带通曲线，且所述带通曲线可以在所述增益芯片的增益曲线范围内调节移动。
  20. 如权利要求19所述的基于法布里波罗F-P光腔的外腔激光器，其中：所述带通滤波器具有单一带通峰的带通曲线，所述带通滤波器的单一带通峰的带通曲线宽度与所述F-P光腔的纵模间距FSR之间满足：同一时刻仅有一个所述F-P光腔的纵模完全处于所述带通曲线的内部。
  21. 如权利要求19所述的基于法布里波罗F-P光腔的外腔激光器，其中：所述带通滤波器具有周期性的带通曲线，所述带通滤波器的周期性的带通曲线具有与所述F-P光腔不同的FSR,且同一时刻所述带通滤波器仅有一个纵模频率与所述F-P光腔的一个纵模频率对齐。
  22. 如权利要求14-18中任一项所述的基于法布里波罗F-P光腔的外腔激光器，还包括相移器，所述相移器设置于所述激光光源与所述F-P光腔之间或所述激光光源与所述腔外反射镜之间。
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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20070008996A1 (en) * 2005-06-13 2007-01-11 Blair Linville Laser wavelength stabilization for pumping purposes using adjusted Fabry-Perot filter
CN102244358A (zh) * 2011-06-02 2011-11-16 天津奇谱光电技术有限公司 一种外腔式可调谐激光器
CN102709811A (zh) * 2012-06-19 2012-10-03 中国科学院半导体研究所 一种实现频率自锁定的分布反馈外腔窄线宽半导体激光器
CN102868090A (zh) * 2012-09-28 2013-01-09 武汉光迅科技股份有限公司 具有灵活波长栅格调谐功能的外腔可调激光器
WO2019096408A1 (en) * 2017-11-17 2019-05-23 Cobolt Ab External cavity diode laser arrangement

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE69527830T2 (de) * 1994-11-14 2003-01-02 Mitsui Chemicals Inc Wellenlängenstabilisierter Lichtquelle
US5949801A (en) * 1998-07-22 1999-09-07 Coretek, Inc. Tunable laser and method for operating the same
CN107534505B (zh) * 2015-04-28 2019-05-28 华为技术有限公司 一种多载波激光器以及产生多载波光的方法
CN105529613A (zh) * 2016-01-15 2016-04-27 北京工业大学 一种852nm超窄线宽外腔半导体激光器

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20070008996A1 (en) * 2005-06-13 2007-01-11 Blair Linville Laser wavelength stabilization for pumping purposes using adjusted Fabry-Perot filter
CN102244358A (zh) * 2011-06-02 2011-11-16 天津奇谱光电技术有限公司 一种外腔式可调谐激光器
CN102709811A (zh) * 2012-06-19 2012-10-03 中国科学院半导体研究所 一种实现频率自锁定的分布反馈外腔窄线宽半导体激光器
CN102868090A (zh) * 2012-09-28 2013-01-09 武汉光迅科技股份有限公司 具有灵活波长栅格调谐功能的外腔可调激光器
WO2019096408A1 (en) * 2017-11-17 2019-05-23 Cobolt Ab External cavity diode laser arrangement

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