wherein W is the total energy stored in the laser resonant cavity; dW/dt is the loss rate of photon energy in the laser resonant cavity, namely the energy lost in unit time; v is₀The center frequency of the generated laser light.

The Q-switching technology compresses laser energy generated by a laser into pulses with extremely narrow widths to be emitted by adjusting the Q value of a laser resonant cavity, so that the peak power of the generated laser is improved by several orders of magnitude, and the laser with narrow pulse width and high peak value is obtained. In particular, the peak power of the laser can reach megawatt level (10) by the Q-switching technology⁶W) or more, pulse width compression to nanosecond (10)^-9s) of the pulse.

In general, the adjustment of the Q value of the laser resonant cavity is realized by changing the loss in the cavity. Specifically, when the pumping starts, the loss of the laser resonant cavity is large, that is, the Q value of the laser resonant cavity is reduced, so that the gain medium accumulates the population of the inversion; after pumping for a certain time, the loss of the laser resonant cavity is suddenly reduced, namely the Q value of the laser resonant cavity is increased, so that the accumulated inversion population completes stimulated radiation in a short time to form optical pulses with narrow pulse width and high peak power.

In the Q-switching technology, the laser resonant cavity is in a high-loss and low-Q-value state in most of the pumping process, so that the resonant cavity has a high threshold value and cannot start oscillation, and the population number in the gain medium, which is positioned at an upper energy level and realizes inversion, is continuously accumulated; when the number of the accumulated particles for realizing the inversion reaches a certain value, the loss of the resonant cavity suddenly drops, the Q value suddenly rises, and the threshold value of the laser oscillation is rapidly reduced; then laser oscillation begins to be established in the laser resonant cavity; because the number of particles accumulated during the loss reduction and Q value increase is large, the stimulated radiation is enhanced very quickly at the moment, and the energy stored in the gain medium is released in a short time, so that high-peak narrow-pulse-width laser is formed.

Specifically, the Q-switching unit 130 includes a saturable absorber. The saturable absorber is an optical device with definite loss, when the incident light intensity exceeds the threshold value of the saturable absorber, the optical loss becomes small, the transmittance is increased, and the Q value of the laser resonant cavity is increased.

In this embodiment, the material of the saturable absorber in the Q-switching unit includes: at least one of YAG, carbon nanotube and graphene. Preferably, the material of the saturable absorber is at least one of carbon nanotubes or graphene. The carbon nano tube or the graphene has good heat conductivity, and can effectively improve the heat conduction and heat dissipation effects of components in the laser resonant cavity.

In this embodiment, the gain medium is a microchip type gain medium; the saturable absorber is a microchip type saturable absorber, that is, the size of the gain medium and the size of the saturable absorber are small in the light propagation direction, and are about centimeter magnitude.

As shown in fig. 1, the gain medium and the saturable absorber are bonded to each other, that is, a surface of the gain medium in thegain unit 120 facing the Q-switching unit 130 and a surface of the saturable absorber in the Q-switching unit 130 facing thegain unit 120 are bonded to each other in contact with each other.

The gain medium and the saturable absorber are both processed into a microchip type and are attached together, so that the laser has a compact structure, the size of a laser resonant cavity can be effectively controlled, and the realization of high repetition frequency, narrow pulse width and high peak power is facilitated.

Thelight splitting unit 140 is used to generate anoutgoing laser beam 141 or a plurality of tuningbeams 142 of different wavelengths. Wherein theemergent laser light 141 is output light of the laser; the tuning light 142 is made to resonate in the laser resonator.

Specifically, the light beams emitted from thegain unit 120 and the Q-switching unit 130 are projected onto thelight splitting unit 140, and thelight splitting unit 140 generates the emittedlaser beam 141 or the tuning light 142 with a plurality of different wavelengths based on the light beams.

In this embodiment, thelight splitting unit 140 includes: and (4) a grating. The grating is used as the light splitting device, so that the light splitting effect of the generatedemergent laser 141 or the plurality of tuninglights 142 can be effectively ensured, and the difference of the propagation directions of the tuninglights 142 among different wavelengths can be made large enough through the selection of a proper grating (such as a small grating constant) to reduce the difficulty in selecting a subsequent scanning unit. However, in other embodiments of the present invention, the splitting unit may be configured as other optical devices capable of splitting a plurality of tuning lights, such as a prism.

As shown in fig. 1, thelight splitting unit 140 is a transmissive grating. The implementation of light splitting by using a transmissive grating in thelight splitting unit 140 is merely an example. In other embodiments of the present invention, the grating may include: at least one of a reflective grating or a transmissive grating.

Furthermore, in this embodiment, the grating includes: a-1 order high diffraction efficiency grating or a +1 order high diffraction efficiency grating. When the grating is a-1 st order high diffraction efficiency grating, thelight splitting unit 140 generates the emittedlaser light 141 in the exit direction of 0 th order light of the-1 st order high diffraction efficiency grating, and generates the tuninglights 142 in the exit direction of-1 st order diffraction light of the-1 st order high diffraction efficiency grating; when the grating is a + 1-order high diffraction efficiency grating, thelight splitting unit 140 generates the emission laser light in the 0-order light emission direction of the-1-order high diffraction efficiency grating, and generates the plurality of tuninglights 142 based on the + 1-order diffraction light emission direction of the + 1-order high diffraction efficiency grating.

Thelight splitting unit 140 implements light splitting by using a-1 level high diffraction efficiency grating or a +1 level high diffraction efficiency grating, which can effectively improve the energy of the tuninglights 142 generated by thelight splitting unit 140, reduce the energy of the output light of thelight splitting unit 140, and equivalently reduce the output transmittance of the laser resonant cavity, thereby effectively reducing the loss of the laser resonant cavity, reducing the upper level particle number accumulation, and effectively controlling the pulse energy of the output light.

Laser repetition frequency (repetition frequency) versus pump power and single pulse energy and laser resonator cavity length:

wherein L is the cavity length of the laser resonant cavity.

Therefore, the shorter the laser resonant cavity length is, the higher the laser repetition frequency is; under the same pumping power, the energy of a single pulse is relatively reduced, and a pulse with higher repetition frequency can be output. Therefore, thelight splitting device 140 is provided with a-1 st high diffraction efficiency grating or a +1 st high diffraction efficiency grating to realize light splitting, and the energy of output light can be controlled, which is beneficial to obtaining high repetition frequency pulses.

In addition, since the Q-switching unit 130 includes a saturable absorber, the loss of the laser resonator can be controlled by the selection of the saturable absorber and the selection of theoptical splitting unit 140, which not only can effectively improve the flexibility of the repetition frequency setting of the laser of the present invention, but also is beneficial to expanding the selection range of the saturable absorber and the optical splitting device.

Specifically, the grating may be a deep-etched binary phase grating. When the grating is a-1-level high diffraction efficiency grating, the-1-level broadband diffraction efficiency of the-1-level high diffraction efficiency grating is greater than or equal to 95%; when the grating is a + 1-level high diffraction efficiency grating, the + 1-level broadband diffraction efficiency of the + 1-level high diffraction efficiency grating is greater than or equal to 95%.

With continued reference to fig. 1, the laser further includes a resonant reflectingsurface 150 located between thegain unit 120 and thepumping unit 110 and ascanning unit 160 located in the optical path of the plurality of tuning lights 142.

Theresonant reflection surface 150 and thescanning unit 160 are matched to form two reflection surfaces of a laser resonant cavity, so that thegain unit 120, the Q-switching unit 130 and thebeam splitting unit 140 are located on an optical path between theresonant reflection surface 150 and thescanning unit 160, that is, thegain unit 120, the Q-switching unit 130 and thebeam splitting unit 140 are located between the two reflection surfaces of the laser resonant cavity.

It should be noted that, as shown in fig. 1, in this embodiment, the resonant reflectingsurface 150 and thescanning unit 160 are used to form two reflecting surfaces of a laser resonant cavity, and thegain unit 120, the Q-switching unit 130, and thebeam splitting unit 140 are located in an optical path in the laser resonant cavity. This is merely an example. In other embodiments of the present invention, based on specific requirements, other optical components may be further disposed in the optical path in the laser resonant cavity to implement optical path adjustment.

In this embodiment, the surface of the gain medium facing thepumping unit 110 is plated with anoptical film 151 to form the resonant reflectingsurface 150, and the surface of the gain medium facing thepumping unit 110 is formed with the resonant reflectingsurface 150, so that the size of the laser can be effectively controlled, the cavity length of the laser resonant cavity can be reduced, the structure is compact, and the realization of high repetition frequency, narrow pulse width and high peak power is facilitated; and theoptical coating 151 may be configured as a film layer having an effect of increasing the transmittance of the pump light and the reflectivity of the resonant reflectingsurface 150, thereby achieving the purpose of improving the performance of the laser resonator. However, in other embodiments of the present invention, the resonant reflecting surface may also be flexibly disposed by other methods.

Thescanning unit 160 is configured to form a reflection surface of the laser resonator, and is further configured to select one of the tuninglights 142 with different wavelengths, and return the selected tuning light 142 to the original optical path to form resonance.

As shown in fig. 1, in this embodiment, thescanning unit 160 changes the incident angles of the tuninglights 142 in a swinging or rotating manner, and returns the tuning light 142 that is vertically incident according to the original optical path, and the tuning light is projected to the resonant reflectingsurface 150 through thelight splitting unit 140 to form a resonance of the tuning light with a corresponding wavelength in the laser resonator. The selection of the tuning light 142 is realized by the swinging or rotating of thescanning unit 160, the mechanical structure is simple, and the speed of the selection of the tuning light 142 can be controlled by setting the swinging or rotating frequency, which is beneficial to flexibly realizing high-speed wavelength tuning.

The light beams emitted from thegain unit 120 and the Q-switching unit 130 are projected onto thelight splitting unit 140, and thelight splitting unit 140 generates a plurality of tuninglights 142 with different wavelengths based on the light beams. Wherein the different wavelengths of tuning light 142 have different propagation directions.

Since the propagation directions of the tuninglights 142 with different wavelengths are different, the incident angles of the tuninglights 142 with different propagation directions projected onto thescanning unit 160 are changed along with the swing or rotation of thescanning unit 160. At t_iAt the moment, when a tuning light is vertically incident on thescanning unit 160, the vertically incident tuning light is reflected by thescanning unit 160 and returns according to the original optical path; since the tuning light that is vertically incident returns along the original optical path, after being projected to thelight splitting unit 140, the tuning light is again projected to the Q-tuning unit 130 and thegain unit 120, and is finally projected to the resonant reflectingsurface 150, so as to be reflected back and forth in the optical path between the resonant reflectingsurface 150 and thescanning unit 160, that is, resonance is formed in the laser resonator.

Referring collectively to fig. 2-4, the embodiment of the laser shown in fig. 1 is shown with thescanning unit 160 scanning the plurality of tuninglights 142 λ₀、142λ₁、142λ₂… …, and returning the tuning light according to the original light path.

As in fig. 2 to 4, at t₀、t₁、t₂At time … …, the wavelength is λ₀、λ₁、λ₂… … tuned light 142 λ₀、142λ₁、142λ₂… … are respectively vertically incident on thescanning unit 160, and are returned by thescanning unit 160 according to the original optical path until they are projected on theresonant reflection surface 150 to form resonance. Thus at t₀、t₁、t₂… …, the laser resonant cavities are respectively formed with a wavelength of lambda₀、λ₁、λ₂… … tuned light 142 λ₀、142λ₁、142λ₂… …, i.e. the laser cavity is capable of achieving resonance of different wavelengths of light at different times, thereby achieving wavelength tuning of the laser.

It can be seen that the speed of wavelength tuning of the laser is the same as the speed of wavelength tuning of thescanning unit 160 for the different wavelengths of light 142 λ₀、142λ₁、142λ₂… … selecting a speed correlation. In this embodiment, thescanning unit 160 tunes the light 142 λ for different wavelengths₀、142λ₁、142λ₂… … is related to the speed at which thescanning unit 160 oscillates or rotates.

Therefore, thescanning unit 160 includes a galvanometer. A vibrating mirror with high vibration frequency capable of rapidly changing the plurality of tuninglights 142 lambda₀、142λ₁、142λ₂… … at the plurality of tuning light 142 λ₀、142λ₁、142λ₂… …, thereby changing the tuning light of the laser oscillation formed in the laser resonant cavity at high speed, thereby realizing high-speed wavelength tuning. Moreover, thescanning unit 160 may include a MEMS galvanometer, so that the volume of thescanning unit 160 can be effectively reduced, which is beneficial to improve the integration level of the laser.

In this embodiment, the laser further includes thegain unit 120 and the Q-switching unit 130, and thegain unit 120 and the Q-switching unit 130 are located on an optical path of a resonance formed by the tuning light in the laser resonant cavity. Therefore, when the intensity of the tuning light forming resonance in the laser cavity is higher than the preset output threshold, thelight splitting unit 140 generates the outgoing laser light based on the tuning light forming resonance. Wherein the preset output threshold is several times or even ten times of the saturation absorption light intensity of the saturable absorber.

The loss of the laser resonant cavity is related to the saturation absorption light intensity of the saturable absorber, the loss of the laser resonant cavity can be influenced by the selection of the saturable absorber, the threshold value of the laser resonant cavity is controlled, the accumulated number of upper energy level particles is controlled, and then under the same pumping power, the repetition frequency of the laser is improved, and proper peak power and single pulse energy are obtained, so that the consideration of the detection distance and the detection frequency is realized.

Specifically, on the one hand, the selected tuning light is reflected back and forth in the optical path between the resonantreflective surface 150 and thescanning unit 160 to form resonance in the laser resonator; thegain unit 120 is located in the optical path of the laser resonator, and with the input of the pump light, the particles in the gain medium are continuously excited to a high energy state, so that the particles realizing inversion are continuously accumulated and increased; the intensity of the light reflected back and forth between the resonantreflective surface 150 and thescanning unit 160 gradually increases.

On the other hand, the Q-switching unit 130 has a saturable absorber therein. As previously mentioned, a saturable absorber is a nonlinear absorption medium whose absorption coefficient is not constant. Under the action of stronger laser, the absorption coefficient of the saturable absorber is reduced until saturation along with the increase of light intensity, and the saturable absorber has the characteristic of transparency to light.

Further, the relation between the absorption coefficient of the saturable absorber and the light intensity is as follows:

wherein alpha is₀The absorption coefficient is when the light intensity is small (when the light intensity I tends to 0); i is_sIs the saturation absorption intensity of the saturable absorber, related to the material of the saturable absorber; i is the intensity of light projected onto the saturable absorber.

Therefore, when the light intensity projected to the saturable absorber is comparable to the saturated absorption light intensity, the absorption coefficient is gradually reduced, and the transmittance is gradually increased; when the light intensity projected on the saturable absorber reaches a certain value, the absorption of the saturable absorber on the light intensity reaches a saturation (absorption minimum) value, the absorption coefficient of the saturable absorber decreases suddenly, the transmittance increases sharply, and the saturable absorber is suddenly bleached to become transparent.

It can be seen that the selected tuning light, during the back and forth reflection between thescanning unit 160 and the resonant reflective surface 150:

when the laser resonator starts to reflect back and forth, the autofluorescence in the laser resonator is very weak, the absorption coefficient of the saturable absorber is very large, the transmittance of light is very low, the laser resonator is in a state of high loss and low Q value, although the laser resonator can form resonance, the loss is too high and is larger than the gain, so that laser oscillation cannot be formed, and the excited particles in the gain medium can only be largely maintained in a high energy state, namely, reversed particles are accumulated in the gain medium;

with the continuous input of pump light, excited particles are more and more, the number of reversed particles in the gain medium is further increased, and the autofluorescence in the laser resonant cavity is enhanced;

when the light intensity is increased to the saturation absorption light intensity I of the saturable absorber_sCompared with the prior art, the saturable absorber has the advantages that the absorption coefficient is reduced, the transmittance is gradually increased, the loss of the laser resonant cavity is reduced, and the Q value is improved;

when the light intensity is increased to a certain value and is far higher than the saturation absorption light intensity of the saturable absorber, the absorption coefficient of the saturable absorber tends to zero, the transmittance tends to 1, namely the saturable absorber is changed into transparent, the loss of the laser resonant cavity is suddenly reduced, the Q value is suddenly increased, and the gain of the laser resonant cavity is larger than the loss, so that laser oscillation is formed in the laser resonant cavity.

When laser oscillation is formed, a large amount of inversion particles accumulated in the gain medium and located in a high energy state transition to a low energy state in a short time, thereby forming output laser light; the output laser light is projected to thelight splitting unit 140, and thelight splitting unit 140 generates theoutgoing laser light 141 based on the output laser light.

It should be noted that when the gain in the laser resonant cavity is greater than the loss, laser oscillation can be formed in the laser resonant cavity to form output laser, and then theemergent laser 141 can be formed; and only when the intensity of the tuning light forming resonance in the laser resonant cavity is far higher than the saturation absorption light intensity of the saturable absorber, the saturable absorber can be changed into transparent, so that the gain in the laser resonant cavity is larger than loss, and laser oscillation is formed. Wherein the saturable absorber becomes transparent, and the intensity of the tuning light reflected back and forth when the laser oscillation is formed is related to the specific design of the laser resonant cavity.

In this embodiment, the output threshold is ten times of the saturation absorption light intensity of the saturable absorber, that is, when the difference between the intensity of the tuning light forming resonance in the laser resonator and the saturation absorption light intensity of the saturable absorber is at least one order of magnitude, and the intensity of the tuning light forming resonance in the laser resonator is more than 10 times of the saturation absorption light intensity, the saturable absorber becomes transparent, and the laser oscillation is formed in the laser resonator to generate theemergent laser 141.

It should be noted that the specific structure of the laser shown in fig. 1 is only an example. In other embodiments of the present invention, the laser can further include other components such as an electric circuit, an optical path adjusting component, and the like, which is not limited by the present invention.

Referring to fig. 5, a schematic diagram of an optical path structure of another embodiment of the laser of the present invention is shown.

The present embodiment is the same as the previous embodiments, and the description of the present invention is omitted. The difference between this embodiment and the previous embodiment is that, in this embodiment, thelight splitting device 240 is a reflective grating.

The pump light generated by thepump unit 210 is adjusted in optical path by the pumpoptical element 211, transmitted through the resonant reflectingsurface 250, and then projected to thegain unit 220 and the Q-switching unit 230; the light beams emitted from thegain unit 220 and the Q-switching unit 230 are reflected by thelight splitting unit 240 to form a plurality of tuninglights 242 projected to thescanning unit 260; thescanning unit 260 changes the incident angle of the tuninglights 242 in a swinging or rotating manner, and returns the tuninglights 242 that are vertically incident according to the original optical path, so that resonance is formed in the laser resonant cavity in which the resonant reflectingsurface 250 and thescanning unit 260 serve as two reflecting surfaces; when the intensity of tuning light forming resonance in the laser resonant cavity is increased to a certain value, laser oscillation is formed in the laser resonant cavity to form output laser; thelight splitting unit 240 generatesoutgoing laser light 241 based on the output laser light.

Correspondingly, the invention also provides a laser radar, comprising: a transmitting device comprising the laser of the present invention.

Referring to fig. 1, a schematic diagram of an optical path structure of an embodiment of the lidar of the present invention is shown.

As shown in fig. 1, the lidar comprises a transmitting device comprising a laser of the present invention. The specific technical solution of the laser refers to the embodiments of the laser, and the present invention is not described herein again.

Because the transmitting device comprises the laser which is a tunable laser capable of realizing Q-switching, the transmitting device can generate light with higher peak power and larger pulse energy for detection, and is beneficial to the control of laser radar energy consumption and the expansion of detection distance; moreover, the Q-switching technology of the saturable absorber is utilized, so that the acquisition of high repetition frequency of the laser radar and the realization of high integration are facilitated; in addition, the transmitting device can also realize the tuning of the wavelength, and the laser radar can realize one-dimensional scanning without additionally arranging a device, so that the overall design difficulty of the laser radar can be reduced (for example, two-dimensional scanning can be realized only by a one-dimensional device), and the manufacturing difficulty and the manufacturing cost of the laser radar can be reduced.

It should be noted that the specific structure of the transmitting device shown in fig. 1 is only an example. In other embodiments of the present invention, the transmitting device can further include other components such as an electric circuit, an optical path adjusting component, and the like, which is not limited by the present invention.

As shown in fig. 1, the lidar further includes: alight splitting device 370, thelight splitting device 370 generatingscanning light 371 of different propagation directions based on the wavelength of the light generated by the emitting device.

Thelight splitting device 370 is used to form a plurality ofscanning lights 370 with different propagation directions. Since the emitting device comprises the laser of the present invention, i.e., the emitting device comprises a tunable laser, the emitting device is capable of continuously changing the laser output wavelength within a certain range. Thelight splitting device 370 generates scanned light 371 based on the wavelength of the light produced by the emitting device.

In this embodiment, thelight splitting device 370 is a grating. According to the wavelength variation of the light generated by the emitting device, an appropriate grating is selected, so that the emission directions ofdifferent scanning lights 371 can be appropriate, and an appropriate field angle and an appropriate angular resolution can be obtained. However, in other embodiments of the present invention, the light splitting device may also be at least one of a grating or a prism, which is not limited in the present invention.

In this embodiment, the laser radar is a laser radar that detects based on a time of flight, and the time of flight is obtained in relation to an actual time when the emitting device generates light, and further in relation to a time when the laser oscillation in the laser generates output laser light. Therefore, the lidar further comprises: adetection unit 380, thedetection unit 380 detecting a timing at which the laser oscillation forms the output laser light.

In this embodiment, the detectingunit 380 may include a photodiode. Thedetection unit 380 detects a part of diffracted light generated by thelight splitting unit 140 in the laser in the emitting device to obtain the time when the laser oscillation generates output laser light.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A laser, comprising: the device comprises a pumping unit, a gain unit, a Q-switching unit and a light splitting unit which are sequentially arranged along an optical axis;

the pumping unit generates pumping light;

the gain unit comprises a gain medium, and the gain medium is a microchip type gain medium;

the Q-switching unit comprises a saturable absorber which is a microchip type saturable absorber;

the gain medium and the saturable absorber are attached to each other;

the light splitting unit is a transmission type light splitting unit and generates emergent laser and a plurality of tuning lights with different wavelengths, and the propagation directions of the tuning lights with different wavelengths are different;

the resonant reflection surface, the light splitting unit and the scanning unit are matched to form a laser resonant cavity, the resonant reflection surface is located between the gain unit and the pumping unit, the scanning unit is located on the light paths of the tuning lights with different wavelengths, and the scanning unit selects one tuning light from the tuning lights with different wavelengths and enables the selected tuning light to return according to the original light path.

2. The laser as claimed in claim 1, wherein the scanning unit changes the incident angle of the tuning lights with different wavelengths by swinging or rotating, and makes the tuning light with vertical incidence return to the original optical path, and projects the tuning light to the resonant reflecting surface through the light splitting unit to form the resonance of the tuning light with corresponding wavelength in the laser resonant cavity.

3. The laser of claim 1, wherein the splitting unit generates the outgoing laser light based on the tuned light that forms a resonance when an intensity of the tuned light that forms a resonance in the laser cavity is higher than a preset output threshold.

4. The laser of claim 1, wherein the light splitting unit comprises: a transmissive grating.

5. The laser of claim 4, wherein the grating comprises: -a level 1 or +1 high diffraction efficiency grating;

the light splitting unit generates the emergent laser in the emergent direction of 0-order light of the-1-level high diffraction efficiency grating, and generates the tuning lights with different wavelengths in the emergent direction of-1-level diffraction light of the-1-level high diffraction efficiency grating;

alternatively, the spectroscopic unit generates the emission laser light in the 0 th order light emission direction of the +1 st order diffraction efficiency grating, and generates the plurality of tuning lights having different wavelengths in the +1 st order diffraction light emission direction of the +1 st order diffraction efficiency grating.

6. The laser of claim 5, wherein the level-1 high diffraction efficiency grating has a level-1 broadband diffraction efficiency of 95% or greater;

or the + 1-order broadband diffraction efficiency of the + 1-order high-diffraction-efficiency grating is greater than or equal to 95%.

7. The laser of claim 4, wherein the grating comprises: and deeply etching the binary phase grating.

8. The laser of claim 1, wherein the scanning unit comprises a galvanometer.

9. The laser of claim 1, wherein the scanning unit comprises a MEMS galvanometer.

10. The laser of claim 1, wherein the gain medium comprises: cr, LiSAF, Nd, YAG, Nd, YVO₄Er and Yb co-doped glass and crystalAt least one of the bodies.

11. The laser of claim 1, wherein the saturable absorber material comprises: at least one of YAG, carbon nanotube and graphene.

12. The laser of claim 1, wherein a surface of the gain medium facing the pumping unit is coated with an optical film layer to form the resonant reflecting surface.

13. A lidar, comprising:

a transmitting device comprising a laser as claimed in any one of claims 1 to 12.

14. The lidar of claim 13, further comprising:

a light splitting device that generates scanning light of different propagation directions based on a wavelength of the light generated by the emitting device.

15. The lidar of claim 14, wherein the beam splitting apparatus comprises: at least one of a grating or a prism.

16. The lidar of claim 13, further comprising:

a detection unit that detects a timing at which the laser oscillation is formed.

17. The lidar of claim 16, wherein the detection unit comprises: a photodiode.