CN112290367A - Novel frequency-doubling complex transverse mode output micro laser device capable of directly generating pulse Q modulation - Google Patents

Novel frequency-doubling complex transverse mode output micro laser device capable of directly generating pulse Q modulation Download PDF

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Publication number
CN112290367A
CN112290367A CN202011182989.4A CN202011182989A CN112290367A CN 112290367 A CN112290367 A CN 112290367A CN 202011182989 A CN202011182989 A CN 202011182989A CN 112290367 A CN112290367 A CN 112290367A
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China
Prior art keywords
crystal
frequency
transverse mode
laser
doubling
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Pending
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CN202011182989.4A
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Chinese (zh)
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张子龙
高原
赵长明
张海洋
赵苏怡
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Beijing Institute of Technology BIT
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Beijing Institute of Technology BIT
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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
    • H01S3/106—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity
    • H01S3/108—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity using non-linear optical devices, e.g. exhibiting Brillouin or Raman scattering
    • H01S3/109—Frequency multiplication, e.g. harmonic generation
    • 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
    • H01S3/1112—Passive mode locking
    • H01S3/1115—Passive mode locking using intracavity saturable absorbers
    • H01S3/1118—Semiconductor saturable absorbers, e.g. semiconductor saturable absorber mirrors [SESAMs]; Solid-state saturable absorbers, e.g. carbon nanotube [CNT] based
    • 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
    • H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
    • H01S3/16—Solid materials
    • H01S3/163—Solid materials characterised by a crystal matrix
    • H01S3/164—Solid materials characterised by a crystal matrix garnet
    • H01S3/1643—YAG

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Optics & Photonics (AREA)
  • Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Nanotechnology (AREA)
  • Nonlinear Science (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Lasers (AREA)

Abstract

The invention relates to a novel frequency-doubling complex transverse mode output micro laser device capable of directly generating pulse Q modulation. The device comprises a gain crystal, a saturable absorber, a frequency doubling crystal and a heat sink. The gain crystal is Nd-YAG crystal for generating fundamental frequency light, the saturable absorber is Cr-YAG crystal for realizing passive Q-switching to generate pulse output, and the frequency doubling crystal is LiTaO3And the crystal is used for frequency doubling of the fundamental frequency light and multiplication of the number of transverse mode orders. One side of the gain crystal and one side of the frequency doubling crystal form a resonant cavity, and copper heat sinks are attached to the outer sides of the gain crystal and the frequency doubling crystal so as to increase the heat conduction efficiency of the micro-sheet and ensure the normal work of the device. The device can effectively obtain high-order transverse mode laser output, and is simple, compact and stable in structure.

Description

Novel frequency-doubling complex transverse mode output micro laser device capable of directly generating pulse Q modulation
The technical field is as follows:
the present invention relates to a microchip pulse laser technology and a frequency doubling laser technology, particularly to a microchip pulse laser technology capable of directly generating a complex transverse mode.
Background art:
the laser beam output by the complex transverse mode has wide application in the fields of particle manipulation, optical communication, 3D printing and the like. In particle manipulation, the laser spot shape is the main factor affecting the directional manipulation of particles; in the field of optical communication, the orbital angular momentum carried by photons in the vortex beam is proportional to the beam order l. The common method for obtaining high-order transverse mode laser output is mainly to add phase elements or absorption rings and other elements in a resonant cavity to obtain high-order transverse mode output, and the method is completely different from the method, simpler, more compact and more stable in structure.
The invention content is as follows:
the invention utilizes the gain medium with a microchip structure to generate initial frequency laser. Due to the saturable absorber, the laser only can penetrate through the saturable absorber when the initial frequency laser power is high enough, and the first-class phase matching frequency multiplication is realized through the frequency multiplication crystal to obtain the pulse laser output. In the process of laser frequency doubling, the frequency of the laser is changed to be twice of the original frequency, and the transverse mode order of the laser is also changed to be twice of the original order, so that high-order complex transverse mode output is realized.
The technical scheme adopted by the invention for solving the technical problems is as follows:
the laser resonator is composed of three crystals: two of which are a gain medium and a saturable absorber for generating pulsed laser light. The other is a frequency doubling crystal, which doubles the frequency of the output of the microchip laser and doubles the order of the transverse mode. In order to reduce the volume of the laser and facilitate the integration of the laser, the three crystals all adopt a microchip structure. The thickness is not more than 1mm, and the cross section area is 5 mm.
When the laser power is low for the initial 1064nm wavelength inside the cavity, the laser cannot pass through the saturable absorber. When the laser peak power is high enough, the laser with the initial 1064nm wavelength passes through the saturable absorber and passes through the frequency doubling crystal to obtain frequency doubling pulse laser output with the wavelength of 532nm, and the transverse mode order of the output laser is doubled at the same time. Thereby realizing the output of frequency doubling pulse high-order transverse mode laser. The gain crystal and the frequency doubling crystal are externally attached with copper heat sinks to accelerate the heat conduction of the microchip, ensure the temperature of the crystal to be constant and realize stable frequency conversion.
The invention has the beneficial effects that:
the technology can directly generate the pulse high-order transverse mode light beam without a special pumping source and a light beam control element. In addition, the cross section area and the thickness of the gain crystal, the saturable absorber and the frequency doubling crystal with the microchip structure can be controlled in millimeter magnitude, the volume of the laser is greatly reduced, and integration is facilitated.
Description of the drawings:
fig. 1 is a three-view diagram of the structure of a gain medium and a frequency doubling crystal, and the main structure is as follows: gain medium, saturable absorber, frequency doubling crystal, and resonator cavity mirror.
FIG. 1 is illustrated symbolically as follows: 1, a gain medium; 2, a saturable absorber; 3, frequency doubling crystals; 4, a resonant cavity mirror 1; 5, a resonant cavity mirror 2; 6, heat sink 1; 7, heat sink 2.
The specific implementation mode is as follows:
the resonant cavity of the microchip laser consists of a gain crystal Nd, a YAG crystal, a saturable absorber Cr, a YAG crystal and a frequency doubling crystal LiTaO3The crystal is compounded. The three adopt a microchip structure, the thickness is not more than 1mm, and the cross section area is 5 mm. Are adhered together in the form of optical cement. The end face of the gain crystal is coated with a film to form the resonant cavity mirror 1 which has high transmittance to pumping light of 808nm and high reflectance to fundamental frequency light of 1064nm and frequency doubling light of 532 nm. And the end face of the frequency doubling crystal is coated with a film to form a resonant cavity mirror 2 which is highly reflective to the 1064nm fundamental frequency light and highly transparent to 532nm laser of the frequency doubling light. The gain medium, the saturable absorber, the frequency doubling crystal, the resonant cavity mirror 1 and the resonant cavity mirror 2 form a resonant cavity. The saturable absorber can be similar to a two-level system, the absorption coefficient of the saturable absorber is reduced along with the increase of light intensity, when the light intensity is large, the absorption coefficient is zero, and almost all incident light penetrates through the saturable absorber. When the pumping light just enters from the end face of the resonant cavity mirror 1, the laser cannot start oscillation due to the large absorption coefficient of the saturable absorber and the large loss of the resonant cavity. The amplified spontaneous radiation gradually increases along with the accumulation of the number of inversion concentration in the laser working substance, when the light intensity increases, the absorption coefficient of the saturable absorber is obviously reduced, the laser gain is greater than the loss, and the laser starts to oscillate. As the intensity of light increases, the absorption coefficient continues to decrease, causing the laser light to increase more rapidly. When the light intensity is highUpon reaching saturation, the gain factor decreases, eventually leading to laser extinction. This cycle is repeated, producing a sequence of pulses. After pulse laser is propagated into frequency doubling crystal and the first kind of phase matching condition (oo-e) is reached, frequency doubling effect is produced, the laser frequency is twice of original frequency, and the transverse mode order is twice of original order, LGp,lAnd (1064nm) light beam l is changed into 2l, the wavelength is changed into 532nm, wherein l is the transverse mode order of the initial light beam, and pulse frequency doubling high-order transverse mode laser output is realized. A layer of copper heat sink is attached to the outside of the gain crystal and the frequency doubling crystal, the aperture with the diameter of 3mm is arranged in the center of the heat sink and used for light transmission, the heat sink is used for accelerating the heat conduction of the microchip, the temperature of the crystal is ensured to be constant, the influence of the thermal effect of the crystal is reduced, and stable frequency conversion is realized.

Claims (4)

1. A miniature laser device for outputting pulse Q-switched frequency-doubled complex transverse mode output is characterized in that: gain crystal, absorption crystal, frequency doubling crystal and heat sink on two sides of the microchip, wherein:
the gain crystal is used for converting pump light with wavelength of 808nm into laser with wavelength of 1064 nm;
the absorption crystal is used for passively adjusting Q and generating pulse output;
the frequency doubling crystal is used for doubling the frequency of 1064nm laser and doubling the number of transverse modes of the laser to obtain high-order 532nm laser;
and the heat sink is used for reducing the heat conduction of the microchip crystal and ensuring the constant temperature of the crystal.
2. The miniature laser device for outputting pulsed Q-switched frequency-doubled complex transverse mode output according to claim 1, further characterized in that: the gain crystal is plated with a high reflection film for 1064nm and 532nm and an antireflection film for 808nm, and the frequency doubling crystal is plated with a high reflection film for 1064nm and a high transmission film for 532 nm.
3. The miniature laser device for outputting pulsed Q-switched frequency-doubled complex transverse mode output according to claim 1, further characterized in that: the gain crystal adopts Nd-YAG crystal, the absorption crystal adopts Cr-YAG crystal, and the frequency doubling crystal adopts LiTaO3And (4) crystals.
4. The miniature laser device for outputting pulsed Q-switched frequency-doubled complex transverse mode output according to claim 1, further characterized in that: in Nd, YAG crystal and LiTaO3Copper heat sinks are attached to two sides of the crystal.
CN202011182989.4A 2020-10-29 2020-10-29 Novel frequency-doubling complex transverse mode output micro laser device capable of directly generating pulse Q modulation Pending CN112290367A (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5394413A (en) * 1994-02-08 1995-02-28 Massachusetts Institute Of Technology Passively Q-switched picosecond microlaser
CN200947526Y (en) * 2006-09-11 2007-09-12 福州高意通讯有限公司 Semiconductor end pumped micro laser
CN105048274A (en) * 2015-08-24 2015-11-11 山东大学 Passive Q-switched pulse-type self-frequency doubling green light laser
CN109698461A (en) * 2019-03-11 2019-04-30 山东大学 A kind of passive Q-adjusted pulsed is from frequency doubling green light laser
CN210201151U (en) * 2019-08-06 2020-03-27 河北工业大学 All-solid-state green laser

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5394413A (en) * 1994-02-08 1995-02-28 Massachusetts Institute Of Technology Passively Q-switched picosecond microlaser
CN200947526Y (en) * 2006-09-11 2007-09-12 福州高意通讯有限公司 Semiconductor end pumped micro laser
CN105048274A (en) * 2015-08-24 2015-11-11 山东大学 Passive Q-switched pulse-type self-frequency doubling green light laser
CN109698461A (en) * 2019-03-11 2019-04-30 山东大学 A kind of passive Q-adjusted pulsed is from frequency doubling green light laser
CN210201151U (en) * 2019-08-06 2020-03-27 河北工业大学 All-solid-state green laser

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