Miniature mid-infrared laser based on double microdisks

Abstract

A miniature mid-infrared laser based on double microdisks, comprising a laser source (1), a coupler (2), an echo wall microdisk laser (3), and an echo wall microdisk optical parametric oscillator (4).

Description

[0001] This application relates to the field of mid-infrared laser technologies, and in particular to a miniature mid-infrared laser based on double microdisks. BACKGROUND OF THE INVENTION

[0002] Mid-infrared lasers with wavelengths range from 3 pm to 5 pm are most suitable for infrared spectral analyses, so that they are widely applicable in medicine, biology, and other fields. Moreover, the mid-infrared laser is also widely applicable in many aspects, such as meteorological monitoring, space optical communication, laser ranging, laser radar, laser guidance, and remote sensing, because the mid-infrared laser has a strong atmospheric penetration capability.

[0003] Among a lot of technical solutions for generating long-wave infrared band light sources, using a near-infrared laser as a pump light source, and achieving frequency down-conversion through an optical parametric effect is a solution for obtaining infrared lasers with long waves of 3-5 pm. Technical approaches of the solution include differential frequency (DF), optical parametric generation (OPG), optical parametric oscillation (OPO), and optical parametric amplifiers (OPA). Compared with the DF and OPG technologies, the OPO and OPA technologies are simple in devices and can achieve high repetition frequency and high average power output.

[0004] Based on the foregoing principles, the patent with the publication No. CN 209418978U discloses a high-efficiency mid-infrared continuous tunable optical parametric oscillation laser; the patent with the publication No. CN 106981818B discloses a nanosecond pulse optical parametric amplifier, with locking tunable mid-infrared narrow line-width and sheet micro-cavity near infrared seed light injection; and the patent with the publication No. CN 106992426B discloses an intracavity pump optical parametric oscillator for single-ended output. In the foregoing patents, separate space optical elements, such as resonator mirror, lens, and reflector are used to form main components of a laser, which makes it difficult to apply the laser to the fields with high requirements for weight and volume because the lase has a complex overall structure, a large volume, and heavy weight. SUMMARY OF THE INVENTION

[0005] This application provides a miniature mid-infrared laser based on double microdisks, to resolve the problem that a laser is difficult to be applied in the fields with high requirements on weight and volume due to a complex overall structure, a large volume, and heavy weight of the laser.

[0006] To resolve the foregoing problem, this application adopts the following technical solution: A miniature mid-infrared laser based on double microdisks, including a laser source, a coupler, an echo wall microdisk laser, and an echo wall microdisk optical parametric oscillator, wherein the echo wall microdisk laser is stacked with the echo wall microdisk optical parametric oscillator.

[0007] The coupler includes a first lens, a lower-layer coupling crystal, an upper-layer coupling crystal, and a second lens, and the lower-layer coupling crystal is stacked with the upper-layer coupling crystal.

[0008] The first lens is disposed between the laser source and an incident surface of the lower-layer coupling crystal. The echo wall microdisk laser is tangent to a lower-layer coupling surface of the lower-layer coupling crystal. The echo wall microdisk laser is tangent to an upper-layer coupling surface of the upper-layer coupling crystal. The echo wall microdisk optical parametric oscillator is tangent to the upper-layer coupling surface of the upper-layer coupling crystal. The second lens is coupled to an output surface of the upper-layer coupling crystal.

[0009] The laser source is configured to generate a single-frequency laser. After being coupled and collimated by the first lens, the single-frequency laser is coupled by the lower-layer coupling crystal and enters the echo wall microdisk laser. Pump light is formed after the single-frequency laser is performed with upper energy level transition by the echo wall microdisk laser. The pump light is coupled by the upper-layer coupling crystal and enters the echo wall microdisk optical parametric oscillator. Signal light in a near-infrared band and idle light in a mid-infrared band are generated after the pump light is performed with resonance enhancement in the echo wall microdisk optical parametric oscillator. The signal light and the idle light are output after sequentially passing through the upper-layer coupling crystal and the second lens.

[0010] As a preferred solution, the upper-layer coupling crystal further includes a first reflective surface and a second reflective surface; and both the first reflective surface and the second reflective surface are arc surfaces.

[0011] The pump light enters the upper-layer coupling crystal after being reflected and focused by the first reflective surface and the second reflective surface sequentially.

[0012] As a preferred solution, the miniature mid-infrared laser based on double microdisks further includes a first heating element and a second heating element that are respectively disposed at two sides of the echo wall microdisk laser.

[0013] As a preferred solution, the miniature mid-infrared laser based on double microdisks further includes a third heating element and a fourth heating element that are respectively disposed at two sides of the echo wall microdisk optical parametric oscillator.

[0014] As a preferred solution, the echo wall microdisk laser is made of neodymium-doped yttrium vanadate crystals, and has a thickness of 0.5 mm and a diameter of 1-10 mm.

[0015] As a preferred solution, the echo wall microdisk optical parametric oscillator is made of ferroelectric crystals.

[0016] As a preferred solution, the lower-layer coupling crystal and the upper-layer coupling crystal are made of rutile.

[0017] As a preferred solution, a plane in which the lower-layer coupling surface is located coincides with a plane in which the upper-layer coupling surface is located.

[0018] A distance from the echo wall microdisk laser to the lower-layer coupling surface is 100 nm; and a distance from the echo wall microdisk optical parametric oscillator to the upper-layer coupling surface is 100 nm.

[0019] As a preferred solution, the miniature mid-infrared laser based on double microdisks further includes a metal housing, wherein a heat insulation board is disposed within the metal housing, and an airtight port for filling nitrogen and a cable hole for leading out an electric control line are disposed on the metal housing.

[0020] In practical application, the laser source is configured to generate a single-frequency laser. After being coupled and collimated by the first lens, the single-frequency laser is coupled by the lower-layer coupling crystal and enters the echo wall microdisk laser. The pump light is formed after the single-frequency laser is performed with upper energy level transition by the echo wall microdisk laser. The pump light is coupled by the upper-layer coupling crystal and enters the echo wall microdisk optical parametric oscillator. The signal light in the near-infrared band and the idle light in the mid-infrared band are generated after the pump light is performed with resonance enhancement in the echo wall microdisk optical parametric oscillator. The signal light and the idle light are output after sequentially passing through the upper-layer coupling crystal and the second lens.

[0021] Compared with the prior art, this application has the following beneficial effects: The echo wall microdisk laser and the echo wall microdisk optical parametric oscillator are designed as a stacked double-microdisk structure, and multiple coupling of the laser is achieved by one coupler, so that the mass and volume of the miniature mid-infrared laser based on double microdisks is greatly reduced, meeting high requirements of the laser on weight and volume. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The disclosure of the present invention is described with reference to the accompanying drawings. It should be understood that the accompanying drawings are only for illustrative purposes and are not intended to limit the protection scope of the present invention. In the accompanying drawings, same reference numerals are used to indicate same components.

[0023] FIG. 1 is a schematic diagram of an overall structure of a miniature mid-infrared laser based on double microdisks according to an embodiment of this application.

[0024] FIG. 2 is a schematic diagram of a double microdisk structure of a miniature mid-infrared laser based on double microdisks according to an embodiment of this application.

[0025] FIG. 3 is a schematic structure diagram of a coupler of a miniature mid-infrared laser based on double microdisks according to an embodiment of this application.

[0026] FIG. 4 is a schematic diagram of a linear periodic pattern of an echo wall microdisk optical parametric oscillator according to an embodiment of this application.

[0027] FIG. 5 is a schematic diagram of a fan-shaped periodic pattern of an echo wall microdisk optical parametric oscillator according to an embodiment of this application.

[0028] FIG. 6 is a schematic top view of a structure of a miniature mid-infrared laser based on double microdisks according to this application.

[0029] FIG. 7 is a schematic side view of a structure of a miniature mid-infrared laser based on double microdisks according to this application.

[0030] FIG. 8 is a schematic structural diagram of a housing of a miniature mid-infrared laser based on double microdisks according to an embodiment of this application.

[0031] List of the reference numerals in the drawings: 1 Laser Source 2 Coupler 21 First Lens 22 Lower-Layer Coupling Crystal 221 Incident Surface 222 Lower-Layer Coupling Surface 23 Upper-Layer Coupling Crystal 231 Upper-Layer Coupling Surface 232 Output Surface 233 First Reflective Surface 234 Second Reflective Surface 24 Second Lens 3 Echo Wall Microdisk Laser 4 Echo Wall Microdisk Optical Parametric Oscillator 5 First Heating Element 6 Second Heating Element 7 Third Heating Element 8 Fourth Heating Element 9 Metal Housing 91 Airtight Port 92 Cable Hole DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] It is easy to understand that, according to the technical solutions of the present invention, without changing the substantive spirit of the present invention, a person skilled in the art can propose a plurality of alternative structural modes and implementations. Therefore, the following specific implementations and accompanying drawings are only illustrative descriptions of the technical solution of the present invention, and should not be regarded as a limitation to the whole invention or to the technical solutions of the present invention.

[0033] To meet high requirements of a laser on weight and volume, embodiments of this application provide a miniature mid-infrared laser based on double microdisks. FIG. 1 is a schematic diagram of an overall structure of a miniature mid-infrared laser based on double microdisks according to an embodiment of this application. The miniature mid-infrared laser based on double microdisks includes a laser source 1, a coupler 2, an echo wall microdisk laser 3, and an echo wall microdisk optical parametric oscillator 4. FIG. 2 is a schematic diagram of a double microdisk structure of a miniature mid-infrared laser based on double microdisks according to an embodiment of this application. The echo wall microdisk laser 3 is stacked with the echo wall microdisk optical parametric oscillator 4, to form a double microdisk structure. The echo wall microdisk laser 3 is made of crystals doped with rare earth ions, such as Nd: YAG (yttrium aluminum garnet) and Nd: YVO4 (neodymium doped yttrium vanadate). The echo wall microdisk laser 3 has a thickness of 0.5 mm, and has a diameter of 1-10 mm, wherein a preferred diameter is 3 mm.

[0034] A resonant light wavelength of the echo wall microdisk laser 3 is 1000-1500 nm. For example, the resonant light wavelength can be set to 1064 nm or 1342 nm in practical application. The echo wall microdisk optical parametric oscillator 4 is made of ferroelectric crystals, such as LiNbOs (lithium niobate), LiTaCh (lithium tantalate), KTP (potassium titanium phosphate), or other crystals. A periodic domain structure is generated through a room-temperature electric polarization method, to compensate for phase mismatch during a second-order nonlinear process. Typical polarization patterns are shown in FIG. 4 and FIG. 5. FIG. 4 is a schematic diagram of a linear periodic pattern of an echo wall microdisk optical parametric oscillator according to an embodiment of this application. FIG. 5 is a schematic diagram of a fan-shaped periodic pattern of an echo wall microdisk optical parametric oscillator according to an embodiment of this application. In FIG. 4 and FIG. 5, black and white parts represent domains with opposite polarization directions. The laser source 1 is composed of distributed Bragg reflector (DBR) semiconductor lasers of 808 nm, and outputs a single-frequency laser with a wavelength of 808 nm.

[0035] FIG. 3 is a schematic structure diagram of a coupler of a miniature mid-infrared laser based on double microdisks according to an embodiment of this application. The coupler 2 includes a first lens 21, a lower-layer coupling crystal 22, an upper-layer coupling crystal 23, and a second lens 24. The lower-layer coupling crystal 22 is stacked with the upper-layer coupling crystal 23.

[0036] In practical application, the lower-layer coupling crystal 22 and the upper-layer coupling crystal 23 are made of rutile. The first lens 21 is disposed between the laser source 1 and an incident surface 221 of the lower-layer coupling crystal 22. The echo wall microdisk laser 3 is tangent to a lower-layer coupling surface 222 of the lower-layer coupling crystal 22. The echo wall microdisk laser 3 is tangent to an upper-layer coupling surface 231 of the upper-layer coupling crystal 23. The echo wall microdisk optical parametric oscillator 4 is tangent to the upper-layer coupling surface 231 of the upper-layer coupling crystal 23. The second lens 24 is coupled to an output surface 232 of the upper-layer coupling crystal 23.

[0037] According to the miniature mid-infrared laser based on double microdisks provided in this embodiment of this application, in practical application, the laser source 1 is configured to generate a single-frequency laser. After being coupled and collimated by the first lens 21, the single-frequency laser is coupled by the lower-layer coupling crystal 22 and enters the echo wall microdisk laser 3. Pump light is formed after the single-frequency laser is performed with upper energy level transition by the echo wall microdisk laser 3. The pump light is coupled by the upperlayer coupling crystal 23 and enters the echo wall microdisk optical parametric oscillator 4. Signal light in a near-infrared band and idle light in a mid-infrared band are generated after the pump light is performed with resonance enhancement in the echo wall microdisk optical parametric oscillator 4. The signal light and the idle light are output after sequentially passing through the upper-layer coupling crystal 23 and the second lens 24.

[0038] The echo wall microdisk laser 3 and the echo wall microdisk optical parametric oscillator 4 are designed as a stacked double-microdisk structure, and the laser light is coupled for a plurality of times by one laser 2, so that the mass and volume of the miniature mid-infrared laser based on double microdisks is greatly reduced, thereby meeting high requirements of the laser on weight and volume.

[0039] As shown in FIG. 3, in some embodiments of this application, the upper-layer coupling crystal 23 further includes a first reflective surface 233 and a second reflective surface 234. Both the first reflective surface 233 and the second reflective surface 234 are arc surfaces. The pump light enters the upper-layer coupling crystal 23 after being reflected and focused by the first reflective surface 233 and the second reflective surface 234 sequentially. Description is made below by specific examples. FIG. 6 is a schematic top view of a structure of a miniature mid-infrared laser based on double microdisks according to this application. FIG. 7 is a schematic side view of a structure of a miniature mid-infrared laser based on double microdisks according to this application.

[0040] FIG. 6 is a schematic top view of a structure of FIG. 1. The laser source 1 is a DBR laser with a wavelength of 808 nm, a linewidth of 10 MHz, and an average power of 100 mW. The laser of 808 nm that is output by the laser source 1 is output after being collimated by the first lens 21, and enters the lower-layer coupling crystal 22. A distance from the echo wall microdisk laser 3 to the lower-layer coupling surface 222 is 100 nm. A distance from the echo wall microdisk optical parametric oscillator 4 to the upper-layer coupling surface 231 is 100 nm. The laser of 808 nm forms an evanescent wave at an interface of the lower-layer coupling surface 222 and the echo wall microdisk laser 3, which enters the echo wall microdisk laser 3 and is propagated along an outer annular side wall of the echo wall microdisk laser 3. After absorbing the laser of 808 nm, the Nd: YVO4 crystal generates a laser of 1064 nm through upper energy level transition. Resonance-enhanced pump light is formed in the echo wall microdisk laser 3, and is emitted through a coupling plane. The pump light enters the upper-layer coupling surface 231. The pump light further enters the echo wall microdisk optical parametric oscillator 4 through the upper-layer coupling surface 231 after being reflected and focused by the first reflective surface 233 and the second reflective surface 234 sequentially, and is propagated along an outer side of the echo wall microdisk optical parametric oscillator 4. The laser of 1064 nm in the echo wall microdisk optical 8 parametric oscillator 4 is performed with resonance enhancement. When intensity exceeds a threshold, a laser of 1548.6 nm (signal light) and a laser of 3400 nm (idle light) performed with parametric down-conversion are generated. The generated signal light and idle light are performed with resonance enhancement in the echo wall microdisk optical parametric oscillator 4, and the generated laser of 1548.6 nm and laser of 3400 nm are output through the upper-layer coupling surface 231, the output surface 232, and the second lens 24 sequentially.

[0041] A second-order nonlinear process of the echo wall microdisk optical parametric oscillator 4 is: one photon of 1064 nm is converted into one photon of 1548.6 nm and one photon of 3400 nm through the second-order nonlinear process. According to a phase matching formula, at 27°C, a polarization period of the echo wall microdisk optical parametric oscillator 4 is 30.6 pm. The foregoing period is made according to the pattern in FIG. 5 through a room-temperature electric polarization manner.

[0042] Using FIG. 6 as an example, in the echo wall microdisk laser 3, the laser of 808 nm rotates counterclockwise, and the generated laser of 1064 nm is distributed clockwise and counterclockwise. The clockwise laser of 1064 nm enters the lower-layer coupling crystal 22 after passing through the lower-layer coupling surface 222, and returns along an original path to enter the echo wall microdisk laser 3 again, and changes to counterclockwise rotation. After the foregoing process is repeated for a plurality of times, due to a gain competition effect of the laser, the laser of 1064 nm that rotates counterclockwise becomes stronger and the laser of 1064 nm that rotates clockwise becomes weaker. In this way, unidirectional transmission and unidirectional output effects of the laser of 1064 nm are finally formed in the microdisk laser. Moreover, in the echo wall microdisk optical parametric oscillator 4, due to a nonlinear effect, directions of the generated signal light and idle light are consistent with a direction of a pump laser (1064 nm). Therefore, only the laser transmitted counterclockwise exists.

[0043] Further, a wavelength of the pump laser output by the echo wall microdisk laser 3 needs to coincide with a longitudinal mode of the echo wall microdisk optical parametric oscillator 4, so as to achieve a maximum coupling effect. To this end, in the embodiments of this application, each of the echo wall microdisk laser 3 and the echo wall microdisk optical parametric oscillator 4 has a temperature control device. FIG. 7 is a schematic side view of a structure of FIG. 1. The miniature mid-infrared laser based on double microdisks further includes a first heating element 5 and a second heating element 6 that are respectively disposed at two sides of the echo wall microdisk laser 3, and a third heating element 7 and a fourth heating element 8 that are respectively disposed at two sides of the echo wall microdisk optical parametric oscillator 4. Temperature of the echo wall microdisk laser 3 and the echo wall microdisk optical parametric oscillator 4 is controlled to ensure that the wavelength of the pump laser coincides with the longitudinal mode of the echo wall microdisk optical parametric oscillator 4.

[0044] The first heating element 5, the second heating element 6, the third heating element 7, and the fourth heating element 8 are provided with electric heating wires and temperature sensors (such as PT1000) therein. The temperature of the echo wall microdisk laser 3 is controlled by controlling the first heating element 5 and the second heating element 6, and the temperature of the echo wall microdisk optical parametric oscillator 4 is controlled by controlling the third heating element 7 and the fourth heating element 8, so that a wavelength of the laser of 1064 nm that is output by the echo wall microdisk laser 3 can be aligned with a resonance wavelength of the echo wall microdisk optical parametric oscillator 4, and the signal light and the idle light in the echo wall microdisk optical parametric oscillator 4 can be performed with double resonance.

[0045] FIG. 8 is a schematic structural diagram of a housing of a miniature mid-infrared laser based on double microdisks according to an embodiment of this application. The miniature mid-infrared laser based on double microdisks further includes a metal housing 9. A heat insulation board is disposed within the metal housing 9, and the metal housing 9 is designed to have a sealing structure. Moreover, an airtight port 91 for filling nitrogen and a cable hole 92 for leading out an electric control line are disposed on the metal housing 9. The pressing window 91 can be opened by rotating and sealed repeatedly.

[0046] In view of the above, this application discloses a miniature mid-infrared laser based on double microdisks, which has the following beneficial effects. The echo wall microdisk laser 3 and the echo wall microdisk optical parametric oscillator 4 are designed as a stacked double-microdisk structure, and the laser light is coupled for a plurality of times by one laser 2, so that mass and volume of the miniature mid-infrared laser based on double microdisks is greatly reduced. In this way, a problem that the laser is difficult to be applied in the fields with high requirements on weight and volume due to a complex overall structure, a large volume, and heavy weight of the laser is resolved, thereby meeting high requirements of the laser on weight and volume.

[0047] The technical scope of this application is not limited to the content of the foregoing description. A person skilled in the art can make variants and modifications to the foregoing 5 embodiments without departing from the technical idea of the present invention, and these variants and modifications shall all fall within the protection scope of the present invention.

Claims

1. A miniature mid-infrared laser based on double microdisks, characterized by comprising a laser source (1), a coupler (2), an echo wall microdisk laser (3), and an echo wall microdisk optical parametric oscillator (4), wherein the echo wall microdisk laser (3) is stacked with the echo wall microdisk optical parametric oscillator (4);the coupler (2) comprises a first lens (21), a lower-layer coupling crystal (22), an upper-layer coupling crystal (23), and a second lens (24), and the lower-layer coupling crystal (22) is stacked with the upper-layer coupling crystal (23);the first lens (21) is disposed between the laser source (1) and an incident surface (221) of the lower-layer coupling crystal (22); the echo wall microdisk laser (3) is tangent to a lower-layer coupling surface (222) of the lower-layer coupling crystal (22); the echo wall microdisk laser (3) is tangent to an upper-layer coupling surface (231) of the upper-layer coupling crystal (23); the echo wall microdisk optical parametric oscillator (4) is tangent to the upper-layer coupling surface (231) of the upper-layer coupling crystal (23); and the second lens (24) is coupled to an output surface (232) of the upper-layer coupling crystal (23);the laser source (1) is configured to generate a single-frequency laser, wherein the single-frequency laser is coupled by the lower-layer coupling crystal (22) and enters the echo wall microdisk laser (3) after being coupled and collimated by the first lens (21); pump light is formed after the single-frequency laser is performed with upper energy level transition by the echo wall microdisk laser (3); the pump light is coupled by the upper-layer coupling crystal (23) and enters the echo wall microdisk optical parametric oscillator (4); signal light in a near-infrared band and idle light in a mid-infrared band are generated after the pump light is performed with resonance enhancement in the echo wall microdisk optical parametric oscillator (4); and the signal light and the idle light are output after sequentially passing through the upper-layer coupling crystal (23) and the second lens (24).

2. The miniature mid-infrared laser based on double microdisks according to claim 1, wherein the upper-layer coupling crystal (23) further comprises a first reflective surface (233) and a second reflective surface (234); and both the first reflective surface (233) and the second reflective surface (234) are arc surfaces; andthe pump light enters the upper-layer coupling crystal (23) after being reflected and focusedby the first reflective surface (233) and the second reflective surface (234) sequentially.

3. The miniature mid-infrared laser based on double microdisks according to claim 1, further comprising a first heating element (5) and a second heating element (6) that are respectively disposed at two sides of the echo wall microdisk laser (3).

4. The miniature mid-infrared laser based on double microdisks according to claim 1, further comprising a third heating element (7) and a fourth heating element (8) that are respectively disposed at two sides of the echo wall microdisk optical parametric oscillator (4).

5. The miniature mid-infrared laser based on double microdisks according to claim 1, wherein the echo wall microdisk laser (3) is made of neodymium-doped yttrium vanadate crystals, and has a thickness of 0.5 mm and a diameter of 1-10 mm.

6. The miniature mid-infrared laser based on double microdisks according to claim 1, wherein the echo wall microdisk optical parametric oscillator (4) is made of ferroelectric crystals.

7. The miniature mid-infrared laser based on double microdisks according to claim 1, wherein the lower-layer coupling crystal (22) and the upper-layer coupling crystal (23) are made of rutile.

8. The miniature mid-infrared laser based on double microdisks according to claim 1, wherein a plane in which the lower-layer coupling surface (222) is located coincides with a plane in which the upper-layer coupling surface (231) is located; anda distance from the echo wall microdisk laser (3) to the lower-layer coupling surface (222) is 100 nm; and a distance from the echo wall microdisk optical parametric oscillator (4) to the upperlayer coupling surface (231) is 100 nm.

9. The miniature mid-infrared laser based on double microdisks according to claim 1, further comprising a metal housing (9), wherein a heat insulation board is disposed within the metal housing (9), and an airtight port (91) for filling nitrogen and a cable hole (92) for leading out an electric control line are disposed on the metal housing (9).

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