CN113904205A - Optical waveguide chip based on erbium-doped lithium niobate and mode-locked laser - Google Patents
Optical waveguide chip based on erbium-doped lithium niobate and mode-locked laser Download PDFInfo
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- CN113904205A CN113904205A CN202111088025.8A CN202111088025A CN113904205A CN 113904205 A CN113904205 A CN 113904205A CN 202111088025 A CN202111088025 A CN 202111088025A CN 113904205 A CN113904205 A CN 113904205A
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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
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/11—Mode locking; Q-switching; Other giant-pulse techniques, e.g. cavity dumping
- H01S3/1106—Mode locking
- H01S3/1109—Active mode locking
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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
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/06—Construction or shape of active medium
- H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
- H01S3/0632—Thin film lasers in which light propagates in the plane of the thin film
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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
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/06—Construction or shape of active medium
- H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
- H01S3/0632—Thin film lasers in which light propagates in the plane of the thin film
- H01S3/0637—Integrated lateral waveguide, e.g. the active waveguide is integrated on a substrate made by Si on insulator technology (Si/SiO2)
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Abstract
An optical waveguide chip and mode-locked laser based on erbium-doped lithium niobate, the chip is sequentially provided with a substrate, a silicon dioxide cladding, an erbium-doped lithium niobate film and a radio frequency electrode from bottom to top; etching the erbium-doped lithium niobate thin film by utilizing photoetching to form a ridge-type erbium-doped lithium niobate waveguide; the radio-frequency electrodes are arranged on two sides of the erbium-doped lithium niobate waveguide in parallel. The invention adopts the erbium-doped lithium niobate thin film as the waveguide, not only keeps the low-noise gain characteristic of the erbium-doped waveguide, but also introduces the electro-optic characteristic of the lithium niobate waveguide, meets the gain and modulation requirements required by the active mode-locked laser, and can realize the integrated active mode-locked laser with low noise and continuously adjustable repetition frequency by matching with direct current bias. The electrode spacing is close through the ridge-type erbium-doped lithium niobate waveguide, the required modulation voltage and the electric power consumption are reduced, the strong binding of signal light and pump light mode spots can also increase the overlapping of the signal light and the pump light mode spots, and the pumping efficiency is improved.
Description
Technical Field
The invention relates to a mode-locked laser, in particular to an erbium-doped lithium niobate-based optical waveguide chip and a mode-locked laser.
Background
The integrated mode-locked laser has important application in the fields of optical signal processing, optical frequency combing and the like. The traditional integrated mode-locked laser is mainly based on III-V group semiconductor materials, but the service life of upper-level particles of the semiconductor materials is only nanosecond level, so that the generated mode-locked pulse signals have high noise, and the integrated mode-locked laser cannot be applied to occasions with high requirements on the noise characteristics of the laser, such as high-precision optical signal processing, optical frequency combing and the like. In contrast, the upper-level particle lifetime of erbium-doped waveguides, which can reach the millisecond level, can provide gain while ensuring low-noise operation of mode-locked lasers. Integrated mode-locked lasers based on erbium-doped waveguides were studied by the professor Ippen of the american institute of technology and technology (MIT). However, Ippen teaching team mainly adopts passive mode locking technology, i.e. a saturable absorber is prepared on a chip to realize mode locking operation. The mode locking pulse realized by the scheme can not accurately adjust the repetition frequency, the mode locking is basically carried out at the fundamental frequency, namely only one mode locking pulse runs in the cavity at any moment, the repetition frequency is generally in the order of hundreds of megahertz, and the mode locking pulse can not be used for the application needing a high-speed pulse source.
Therefore, a new mode-locked laser device is needed that can simultaneously achieve both low-noise mode-locking characteristics and tunability to repetition frequencies. In addition, from a practical point of view, the pump light power consumption and the electrical power consumption of the chip must also be sufficiently low.
In addition, several comparative techniques related to the present invention are described and analyzed herein one by one.
The first technology is as follows: an integrated mode-locked laser based on III-V semiconductors, as described above, is not suitable for applications requiring high noise in the laser due to the short lifetime of the upper-level particles and the high noise level.
The second technology is as follows: an integrated passive mode-locked laser based on erbium-doped oxide waveguides, i.e. the solution of the teaching team MIT Ippen mentioned above (Byun, IEEE Photonics Technology Letters 21, 763-. As analyzed above, the repetition frequency tuning is poor, and the repetition frequency is generally in the order of hundreds of mhz, which is difficult to be applied to the scene requiring high-speed pulse source.
The third technology: mode-locked pulses were generated Based on cascaded thin-film lithium niobate modulators (Yu, Photonic-Chip-Based interferometric Pulse Generator, CLEO 2021, sm4l.8). The scheme generates mode-locked pulses through an on-chip cascade intensity modulator and a phase modulator, and belongs to a non-cavity (cavityless) pulse generation technology. The generated mode-locking pulse needs the compression of the dispersion fiber outside the chip to realize the narrow pulse width, and the dispersion compression can not be integrated on the chip at present. In addition, the time domain pulse-to-pulse basis is limited by the rejection ratio of the intensity modulator, which is high.
The fourth technology is as follows: a mode-locked laser based on titanium-diffused erbium-doped lithium niobate (Suche, Integrated Optical Ti: Er: LiNbO Soliton Source, IEEE Journal of Quantum Electronics 33,1642-1646, 1997). This scheme creates a waveguide by titanium diffusion in erbium doped lithium niobate bulk material, followed by application of electrode modulation to generate an actively mode-locked pulse. However, the waveguide formed by titanium diffusion is very wide, so that the electrode spacing is very large, and a very high modulation voltage must be applied to generate a strong enough electric field so as to change the refractive index of lithium niobate through an electro-optic effect to realize effective modulation, and the electric power consumption is very high. The titanium diffusion waveguide has poor restriction on the spot of the signal light and the pump light, so that the signal light and the pump light are not well overlapped, the pumping efficiency is low, and the power consumption of the pump light is high. In addition, the pump light input and the signal light output are on the same side, resulting in the need for an additional wavelength division multiplexer to distinguish between the two, increasing cost.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a mode-locked laser based on an erbium-doped lithium niobate film, which adopts the erbium-doped lithium niobate film on an insulator as a substrate material, forms a waveguide by etching the erbium-doped lithium niobate, and manufactures structures such as a high-speed electrode and the like, thereby realizing the integration of an active mode-locked laser and having wide application prospect.
The technical solution of the invention is as follows:
on one hand, the invention provides an optical waveguide chip based on erbium-doped lithium niobate, which is characterized in that the chip is sequentially provided with a substrate, a silicon dioxide cladding, an erbium-doped lithium niobate thin film and a radio frequency electrode from bottom to top;
etching the erbium-doped lithium niobate thin film by utilizing photoetching to form a ridge-type erbium-doped lithium niobate waveguide;
the radio-frequency electrodes are arranged on two sides of the erbium-doped lithium niobate waveguide in parallel.
An upper cladding layer with the refractive index lower than that of the erbium-doped lithium niobate film is arranged above the erbium-doped lithium niobate waveguide and used for protecting the erbium-doped lithium niobate waveguide and reducing waveguide transmission loss.
The material of the upper cladding is a material transparent in both signal light and pump light bands, and typical materials are silica.
An input end face and an output end face are respectively formed by polishing and coating two end faces of the erbium-doped lithium niobate waveguide, the input end face is coated with a signal light high-reflection film and a pumping light anti-reflection film, and the output end face is coated with a signal light partial reflection film and a pumping light high-reflection film.
The reflectivity of the signal light high-reflection film on the input end surface is more than 99%, the reflectivity of the pump light antireflection film on the pump light is less than 1%, the reflectivity of the signal light partial reflection film on the output end surface is between 5% and 95%, and the reflectivity of the pump light high-reflection film on the pump light is more than 90%.
And connecting areas for bonding external gold wires are arranged at two ends of the radio frequency electrode.
The erbium-doped lithium niobate thin film is in x-cut y-transmission, namely, the normal line of the erbium-doped lithium niobate thin film is an x axis, the propagation direction of an optical signal (along an erbium-doped lithium niobate waveguide) is a y axis, a crystal axis is a z axis, and the modes of the signal light and the pump light in the optical waveguide are transverse electric mode (TE) base modes.
The rf electrode has a transmission impedance of 50 ohms.
On the other hand, the invention also provides a mode-locked laser containing the erbium-doped lithium niobate-based optical waveguide chip, which is characterized by further comprising a pump laser, a mode spot matcher and an external driver;
the pump laser outputs pump light of a single TE mode, and the pump light is coupled to the erbium-doped lithium niobate waveguide through the mode spot matcher;
the module spot matcher is used for matching the module spot output by the pump laser with the module spot of the erbium-doped lithium niobate waveguide;
the external driver supplies power to the pump laser, the output power of the pump laser is adjusted by adjusting the power supply current, and the external driver is connected with the connection areas at two ends of the radio-frequency electrode on the chip in a gold wire bonding mode to provide a radio-frequency modulation signal and direct current bias.
The pump laser has a spectral width of more than 0.5nm, and standing waves are prevented from being formed in the erbium-doped lithium niobate waveguide after the output end face of the chip is reflected.
The mode spot matcher is a single lens, a lens group or a tapered waveguide.
The signal light refers to light having a wavelength within the gain bandwidth of the erbium ion, typically 1530nm and 1550nm, and the pump light refers to light having an energy corresponding to the absorption level of the erbium ion and a wavelength shorter than the wavelength of the signal light, typically 980nm or 1480 nm.
The erbium-doped lithium niobate waveguide is in single-mode transmission to signal light and pump light and works in a single Transverse Electric (TE) mode.
The pump laser is coupled into the erbium-doped lithium niobate waveguide from the input end face of the chip through a spot matcher, an external driver supplies power to the pump laser, the output power of the pump laser is adjusted by adjusting the supply current, and the external driver is connected with connecting areas at two ends of a high-speed electrode on the chip in a gold wire bonding mode to provide a radio frequency modulation signal and direct current bias.
The output of the pump laser is a single TE mode, and the output of the pump laser is still the single TE mode after being coupled to the erbium-doped lithium niobate waveguide through the mode spot matcher; the pump laser should have a certain spectral width, e.g., >0.5nm, to avoid standing waves from forming in the erbium-doped lithium niobate waveguide after the output end face of the chip is reflected, which affects the gain uniformity.
The spot matcher is used for matching the spot output by the pump laser and the spot of the erbium-doped lithium niobate waveguide on the chip and can be a single lens, a lens group, a conical waveguide and other devices.
The port of the external driver connected with the high-speed electrode on the chip has 50 ohm impedance, and the propagation direction of the radio-frequency signal applied to the high-speed electrode is along the positive y direction, namely from the input end face to the output end face of the chip; the frequency of the radio frequency signal is integral multiple of the Free Spectral Range (FSR) of the resonant cavity formed by the erbium-doped lithium niobate waveguide; the direct current bias applied to the high-speed electrode by the external driver is used for adjusting the refractive index of the erbium-doped lithium niobate waveguide, so that the FSR of the resonant cavity is changed, and the generated signal repetition frequency is adjusted.
The working principle of the invention is as follows:
firstly, a pump laser is controlled by an external driver to output certain power, and the certain power is coupled to a chip to provide gain for an erbium-doped lithium niobate waveguide; then, applying a modulation signal on the high-speed electrode through an external driver, wherein the signal frequency is equal to the integral multiple of the FSR of the erbium-doped lithium niobate waveguide resonant cavity, periodic refractive index disturbance can be formed in the resonant cavity due to the electro-optic effect of the lithium niobate, mode-locking operation can be realized according to the active mode-locking principle, and the repetition frequency of the output mode-locking pulse is equal to the frequency of the applied modulation signal; finally, the direct current bias voltage applied to the high-speed electrode is changed through an external driver, the refractive index of the waveguide can be integrally changed by utilizing the electro-optic effect of the lithium niobate, so that the FSR is changed, and the continuous adjustment of the repetition frequency is realized.
Compared with the prior art, the invention has the following advantages:
1. the erbium-doped lithium niobate thin film is used as the waveguide, so that the low-noise gain characteristic of the erbium-doped waveguide is reserved, the electro-optic characteristic of the lithium niobate waveguide is introduced, the gain and modulation requirements required by the active mode-locked laser are met, and the integrated active mode-locked laser with low noise and continuously adjustable repetition frequency can be realized by matching with direct current bias. In addition, the ridge waveguide has a large refractive index difference with the upper and lower cladding materials, so that the mode spot of the signal light and the pumping light is strongly bound, the electrode spacing can be close, and the required modulation voltage and the electric power consumption are greatly reduced. The strong beam-binding of the signal light and the pump light mode spot can also increase the overlapping of the signal light and the pump light mode spot, and the pumping efficiency is improved.
2. Compared with the first comparison technology (an integrated mode-locked laser based on III-V group semiconductors), the invention adopts the erbium-doped waveguide to realize longer service life of upper-level particles and lower noise, and can realize low-noise mode-locked operation.
3. Compared with the second comparison technology (an integrated passive mode-locked laser based on the erbium-doped oxide waveguide), the erbium-doped lithium niobate waveguide can directly provide electro-optical modulation, an additional on-chip saturable absorber is not required to be manufactured, and the repetition frequency can be controlled by the frequency of a modulation signal and direct current bias.
4. Compared with the third comparison technology (based on the mode locking pulse generated by the cascade thin-film lithium niobate modulator), the mode locking pulse is generated by the resonant cavity, the ultrashort pulse can be realized without off-chip dispersion compensation, the base noise between the time domain pulse and the pulse can be filtered out by the resonant cavity, and the low-noise pulse generation is realized.
5. Compared with the fourth comparison technology (the mode-locked laser based on the titanium-diffused erbium-doped lithium niobate), the ridge waveguide is adopted, and the constraint on the optical spot mode field is greatly stronger than that of the titanium-diffused waveguide in the fourth technology, so that the electrode spacing can be greatly reduced, the required electric field intensity can be achieved by using a very low driving voltage, and the electric power consumption is lower. And the overlapping of the signal light and the pumping light in the light spots in the waveguide can be increased, and the pumping efficiency is improved. In addition, the pump light input and the signal light output are on two sides of the chip, and an additional wavelength division multiplexer is not needed.
Drawings
Fig. 1 is a schematic diagram of a mode-locked laser based on an erbium-doped lithium niobate thin film of the present invention.
FIG. 2 is a schematic representation of a chip of the present invention in cross-section xoz.
In the figure: 1-pump laser, 2-spot-size converter, 3-chip, 4-external driver, 31-erbium-doped lithium niobate waveguide, 32-radio-frequency electrode, 33-input end face and coating film, 34-output end face and coating film, 35-silicon dioxide cladding, 36-substrate and 37-upper cladding.
Detailed Description
The invention will be further illustrated with reference to the following figures and examples, without thereby limiting the scope of the invention. Embodiments of the present invention include, but are not limited to, the following examples.
Referring to fig. 1 and fig. 2, fig. 1 is a schematic diagram of a mode-locked laser based on an erbium-doped lithium niobate thin film according to the present invention, and fig. 2 is a schematic diagram of a chip cross-section. As shown in the figure, a mode-locked laser based on erbium-doped lithium niobate thin film is characterized by comprising: the chip 3 is provided with a substrate 36, a silicon dioxide cladding 35 and an erbium-doped lithium niobate thin film 31 from bottom to top in sequence, and the erbium-doped lithium niobate thin film is etched to form a ridge waveguide; manufacturing high-speed radio-frequency electrodes 32 on two parallel sides of the erbium-doped lithium niobate waveguide; a low-refractive-index upper cladding layer 37 covers the erbium-doped lithium niobate waveguide; two end faces of the thin-film lithium niobate waveguide are polished and coated, one end face is called an input end face 33, the other end face is called an output end face 34, the input end face is coated with a signal light high-reflection film and a pump light anti-reflection film, and the output end face is coated with a signal light partial reflection film and a pump light high-reflection film.
The erbium-doped lithium niobate thin film 31 is x-cut y-transmission, that is, the normal line of the erbium-doped lithium niobate thin film is along the x-axis, the optical signal propagation direction (i.e., waveguide direction) is along the y-axis, and the crystal axis is the z-axis.
The upper cladding layer 37 serves to protect the erbium-doped lithium niobate waveguide 31 and reduce waveguide transmission loss, and has a lower refractive index than erbium-doped lithium niobate, a typical material such as silica.
The signal light refers to light having a wavelength within the gain bandwidth of the erbium ion, typically 1530nm and 1550nm, and the pump light refers to light having an energy corresponding to the absorption level of the erbium ion and a wavelength shorter than the wavelength of the signal light, typically 980nm or 1480 nm.
The erbium-doped lithium niobate waveguide 31 is in single-mode transmission with respect to both signal light and pump light, and operates in a single Transverse Electric (TE) mode.
The high-speed electrodes 32 are arranged on two sides of the erbium-doped lithium niobate waveguide along the y direction and made of gold, copper or other high-conductivity metals; the two ends of the electrode 32 are provided with connecting areas for bonding external gold wires; the upper part of the electrode 32 may be covered with the upper cladding material 37 or not (i.e. air is used as the upper cladding), and if the upper cladding is covered, the connection region at the two ends of the electrode needs to be exposed; the high speed electrode 32 impedance is 50 ohms.
The reflectivity of the signal light high-reflection film of the input end face 33 to the signal light is more than 99%, the reflectivity of the pump light antireflection film to the pump light is less than 1%, the reflectivity of the signal light partial reflection film of the output end face 44 to the signal light is between 5% and 95%, and the reflectivity of the pump light high-reflection film to the pump light is more than 90%.
Further, the present invention also includes a peripheral optical device, specifically: the pump laser 1 is coupled into the erbium-doped lithium niobate waveguide 31 from the input end face 33 of the chip 3 through the spot matcher 2, the external driver 4 supplies power to the pump laser 1, the output power of the pump laser 1 is adjusted by adjusting the supply current, and the external driver 4 is connected with the connection areas at two ends of a high-speed electrode 32 on the chip in a gold wire bonding mode to provide a radio frequency modulation signal and direct current bias.
The output of the pump laser 1 is a single TE mode, and the output is still the single TE mode after being coupled to the erbium-doped lithium niobate waveguide 31 through the mode spot matcher 2; the pump laser 1 should have a certain spectral width, e.g., >0.5nm, to avoid standing waves from forming in the erbium-doped lithium niobate waveguide 31 after being reflected at the output end face 34 of the chip, which affects the gain uniformity.
The spot matcher 2 is used for matching the spot output by the pump laser 1 with the spot of the erbium-doped lithium niobate waveguide 31 on the chip, and can be a single lens, a lens group, a tapered waveguide and other devices.
The port of the external driver 4 connected with the high-speed electrode 32 on the chip 3 has 50 ohm impedance, and the propagation direction of the radio-frequency signal applied on the high-speed electrode is along the positive y direction, namely from the input end face 33 to the output end face 34 of the chip; the frequency of the radio frequency signal is an integral multiple of the Free Spectral Range (FSR) of the resonant cavity formed by the erbium-doped lithium niobate waveguide 31; the dc bias applied to the high-speed electrode 32 by the external driver 4 is used to adjust the refractive index of the erbium-doped lithium niobate waveguide 31, thereby changing the FSR of the resonant cavity and realizing the adjustment of the generated signal repetition frequency.
When the erbium-doped lithium niobate waveguide works, firstly, the external driver 4 controls the pump laser 1 to output certain power, and the certain power is coupled to the chip 3 to provide gain for the erbium-doped lithium niobate waveguide 31; then, a modulation signal is applied to the high-speed electrode 32 through the external driver 4, the signal frequency is equal to the integral multiple of the FSR of the erbium-doped lithium niobate waveguide resonant cavity, periodic refractive index disturbance can be formed in the resonant cavity due to the electro-optic effect of the lithium niobate, mode locking operation can be realized according to the active mode locking principle, and the repetition frequency of the output mode locking pulse is equal to the frequency of the applied modulation signal; finally, the direct current bias voltage applied to the high-speed electrode 32 is changed by the external driver 4, and the refractive index of the waveguide can be integrally changed by utilizing the electro-optic effect of the lithium niobate, so that the FSR is changed, and the continuous adjustment of the repetition frequency is realized.
Examples
The thickness of the erbium-doped lithium niobate film is 0.6 micron, the thickness of the silicon dioxide cladding is 2 micron, and the thickness of the substrate silicon material is 400 micron. The depth of erbium-doped lithium niobate waveguide etching is 300 nm. Erbium doped concentration 1 x 1020cm-3. The pump light wavelength is 1480 nm. The metal electrode material is gold and has a thickness of 600 nm. The upper cladding is silica and is 2 microns thick.
Fig. 1 shows a schematic structural diagram of the present invention, and fig. 2 shows a schematic cross-sectional diagram of a chip.
The above description is provided to illustrate a preferred embodiment of the present invention, but not to limit the scope of the invention. All changes, equivalents, and improvements that come within the scope of the invention are intended to be embraced therein.
Claims (13)
1. An optical waveguide chip based on erbium-doped lithium niobate is characterized in that the chip is sequentially provided with a substrate (36), a silicon dioxide cladding (35), an erbium-doped lithium niobate thin film (31) and a radio frequency electrode (32) from bottom to top;
etching the erbium-doped lithium niobate thin film (31) by utilizing photoetching to form a ridge-type erbium-doped lithium niobate waveguide (311);
the radio-frequency electrodes (32) are arranged on two sides of the erbium-doped lithium niobate waveguide (311) in parallel.
2. An erbium-doped lithium niobate-based optical waveguide chip according to claim 1, wherein an upper cladding layer (37) having a refractive index lower than that of the erbium-doped lithium niobate thin film (31) is further provided above the erbium-doped lithium niobate waveguide (311) to protect the erbium-doped lithium niobate waveguide (311) and reduce waveguide transmission loss.
3. An erbium-doped lithium niobate-based optical waveguide chip according to claim 1, wherein the upper cladding layer (37) is made of a material transparent in both signal light and pump light bands.
4. An erbium-doped lithium niobate-based optical waveguide chip according to claim 3, wherein the material of the upper cladding layer (37) is silica.
5. The erbium-doped lithium niobate-based optical waveguide chip of claim 1, wherein an input end face (33) and an output end face (34) are respectively formed by polishing and coating both end faces of the erbium-doped lithium niobate waveguide (311), the input end face (33) is coated with a signal light high reflection film and a pump light antireflection film, and the output end face (34) is coated with a signal light partial reflection film and a pump light high reflection film.
6. The erbium-doped lithium niobate-based optical waveguide chip of claim 5, wherein the reflectivity of the signal light high reflection film of the input end face (33) to the signal light is > 99%, the reflectivity of the pump light antireflection film to the pump light is < 1%, the reflectivity of the signal light partial reflection film of the output end face (34) to the signal light is between 5% and 95%, and the reflectivity of the pump light high reflection film to the pump light is > 90%.
7. An erbium-doped lithium niobate-based optical waveguide chip according to claim 1, wherein connection regions for external gold wire bonding are provided at both ends of the radio frequency electrode (32).
8. An erbium-doped lithium niobate-based optical waveguide chip according to claim 1, wherein the erbium-doped lithium niobate thin film (31) is x-cut y-pass, i.e., a normal line of the erbium-doped lithium niobate thin film is an x-axis, a propagation direction of an optical signal (along the erbium-doped lithium niobate waveguide (311)) is a y-axis, a crystal axis is a z-axis, and modes of the signal light and the pump light in the optical waveguide are transverse electric mode (TE) base modes.
9. An erbium-doped lithium niobate-based optical waveguide chip according to claim 1, wherein the radio frequency electrode (32) has a transmission impedance of 50 ohms.
10. A mode-locked laser comprising an erbium-doped lithium niobate-based optical waveguide chip according to any one of claims 1 to 9, further comprising a pump laser (1), a spot matcher (2), and an external driver (4);
the pump laser (1) outputs pump light of a single TE mode, and the pump light is coupled to the erbium-doped lithium niobate waveguide (311) through the mode spot matcher (2);
the mode spot matcher (2) is used for matching the mode spot output by the pump laser (1) with the mode spot of the erbium-doped lithium niobate waveguide (311);
the external driver (4) supplies power to the pump laser (1), the output power of the pump laser (1) is adjusted by adjusting the power supply current, and the external driver (4) is connected with connecting areas at two ends of the radio-frequency electrode (32) on the chip in a gold wire bonding mode to provide a radio-frequency modulation signal and direct current bias.
11. The mode-locked laser according to claim 10, characterized in that the pump laser (1) has a spectral width >0.5nm, avoiding the formation of standing waves in the erbium-doped lithium niobate waveguide (31) after reflection at the output facet (34) of the chip.
12. The mode-locked laser according to claim 10, wherein the mode spot matcher (2) is a single lens, a lens group or a tapered waveguide.
13. The mode-locked laser according to claim 10, wherein the port of the external driver (4) connected to the rf electrode (32) has an impedance of 50 ohms, and the propagation direction of the rf signal applied to the rf electrode (32) is along the positive y-direction, i.e. from the input facet (33) to the output facet (34); the frequency of the radio frequency signal is integral multiple of free spectral path FSR of the resonant cavity formed by the erbium-doped lithium niobate waveguide (311); the direct current bias applied to (32) by the external driver (4) is used for adjusting the refractive index of the erbium-doped lithium niobate waveguide (311), so that the free spectral path (FSR) of the resonant cavity is changed, and the generated signal repetition frequency is adjusted.
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| CN (1) | CN113904205B (en) |
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| JPH0555680A (en) * | 1991-08-26 | 1993-03-05 | Nippon Telegr & Teleph Corp <Ntt> | Pulse light source |
| US5796764A (en) * | 1996-01-12 | 1998-08-18 | Pirelli Cavi S.P.A. | Rare-earth doped lithium niobate DBR laser |
| US20040100675A1 (en) * | 2002-11-22 | 2004-05-27 | Matsko Andrey B. | Active mode-locked lasers and other photonic devices using electro-optic whispering gallery mode resonators |
| CN110729630A (en) * | 2019-10-11 | 2020-01-24 | 浙江大学 | Laser with high-speed wavelength tuning made of lithium niobate material |
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2021
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JPH0555680A (en) * | 1991-08-26 | 1993-03-05 | Nippon Telegr & Teleph Corp <Ntt> | Pulse light source |
| US5796764A (en) * | 1996-01-12 | 1998-08-18 | Pirelli Cavi S.P.A. | Rare-earth doped lithium niobate DBR laser |
| US20040100675A1 (en) * | 2002-11-22 | 2004-05-27 | Matsko Andrey B. | Active mode-locked lasers and other photonic devices using electro-optic whispering gallery mode resonators |
| CN110729630A (en) * | 2019-10-11 | 2020-01-24 | 浙江大学 | Laser with high-speed wavelength tuning made of lithium niobate material |
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| DAVIDE SCIANCALEPORE等: "Theoretical_modeling_of_FM_mode_locking_in_ErTiLiNbO_sub_3__waveguide_lasers", 《IEEE JOURNAL OF QUANTUM ELECTRONICS》 * |
| YIAN LIU等: "On-chip erbium-doped lithium niobate microcavity laser", 《SCIENCE CHINA，PHYSICS, MECHANICS & ASTRONOMY》 * |
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| CN113904205B (en) | 2023-04-07 |
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