A Design Method of Broadband Mid-Infrared Laser Pulses Based on Non-Collinear Optical Parametric Amplification Technology

Abstract

A design method for broadband mid-infrared laser pulses based on non-collinear optical parametric amplification technology, belonging to the field of laser technology. It is difficult for the known technologies in this field to obtain mid-infrared pulsed laser output with a wide wavelength coverage range and a relatively wide gain bandwidth by using commercially mature ~1μm laser pump sources. The present invention proposes to use Li-based non-oxide crystals under specific type-I non-collinear optical parametric amplification conditions to achieve broadband, i.e., ultrashort pulsed laser amplification. The implementation of the present invention is simple, can provide a wide mid-infrared wavelength coverage range and a wide gain bandwidth, and has good application prospects in the scientific research community and the industrial community.

Description

Technical Field

[0001] A broadband mid-infrared laser pulse design method based on non-collinear optical parametric amplification technology, specifically involving a method for achieving broadband, i.e., ultrashort pulse laser amplification under specific type-I non-collinear optical parametric amplification conditions using Li-based nonlinear crystals, belongs to the field of laser technology. Background Art

[0002] Mid-infrared ultrashort pulse laser light sources have important applications in both the scientific research community and the industrial community, such as in the fields of molecular spectroscopy, strong-field physics, etc. Generating ultrashort pulses is challenging because it is difficult to achieve broadband optical signal amplification. Optical parametric amplification technology (OPA) is one of the main technologies for generating mid-infrared ultrashort pulses. It injects high-energy pump light and low-energy signal light into a nonlinear optical crystal simultaneously. When the phase matching condition is met, energy is transferred from the pump light to the signal light, effectively amplifying the signal light and simultaneously generating an idler light with a longer wavelength. The gain spectral width is an important evaluation parameter in the optical parametric amplification process, which determines the duration of the shortest pulse that can be obtained. Currently, reported mid-infrared optical parametric amplifications mainly focus on oxide crystals, but the longest output wavelength does not exceed 5 μm. There are also reports on mid-infrared optical parametric amplifications around non-oxide crystals, such as ZnGeP 2 , CdSiP 2 and other crystals. However, due to their transparent window limitations, the pump wavelength must be greater than 1.9 μm, and commercially mature ~1 μm laser light sources cannot be used to pump these crystals. Currently, it is difficult for mid-infrared ultrashort pulse lasers to meet practical applications. Summary of the Invention

[0003] The object of the present invention is to provide a broadband mid-infrared laser pulse design method based on non-collinear optical parametric amplification technology. Using lasers with wavelengths of 1.03 μm, 1.064 μm, 1.94 μm, or 2.1 μm as pump sources (corresponding to Yb, Nd, Tm, Ho-doped solid-state lasers respectively), and using supercontinuum as the signal source, the pump light and the signal light are injected into LiGaS 2 (LGS), LiGaSe 2 (LGSe), LiInS 2 (LIS), and LiInSe 2 (LISe) non-oxide crystals at a specific non-collinear angle to generate mid-infrared laser pulses with a typical signal light gain bandwidth of 30 nm - 400 nm (for ~1 μm pump) and 400 nm – 3 μm (for ~2 μm pump), and the wavelength coverage ranges from ~1.15 μm to ~10 μm. The present invention is implemented as follows:

[0004] Step 1: Select LGS, LGSe, LIS, and LISe as the optical parametric amplification crystals, with o s +o i →e p as the optical parametric amplification category. According to and the high light transmittance range of the crystal, calculate the 3D contour maps of the relationship between the non-collinear angle and the wavelengths of the pump light and the signal light when the pump light waves are in the ranges of 0.8 - 2.2 μm (LGS), 0.88 - 2.2 μm (LGSe), 1 - 2.2 μm (LIS), and 1.1 - 2.2 μm (LISe). In the formula, v gs , v gi , λ s , λ i , n s , n i are the group velocities, wavelengths, and refractive indices of the signal light and the idler light respectively, and α is the non-collinear angle, representing the angle between the signal wave vector and the pump wave vector;

[0005] Step 2: According to the calculation results of Step 1, determine that the crystal combinations for realizing broadband optical parametric amplification under the pumping of commercial lasers at 1.03 μm, 1.064 μm, 1.94 μm, and 2.1 μm are LGS (pumped with wavelengths of 1.03 μm and 1.064 μm), LGSe (pumped with wavelengths of 1.03 μm, 1.064 μm, and 1.94 μm), LIS (pumped with wavelengths of 1.03 μm and 1.064 μm), and LISe (pumped with wavelengths of 1.94 μm and 2.1 μm);

[0006] Step 3: According to the results of Step 1 and Step 2, design the central signal light wavelength, idler light wavelength, non-collinear, and phase matching angle parameters for realizing broadband and ultra-broadband optical parametric amplification. In the formula, θ is the phase matching angle, representing the angle between the pump wave vector and the optical axis, λ is the pump wavelength, and n p and n op and n ep are the refractive indices of the o-ray and e-ray of the pump light;

[0007] The effects of the present invention are as follows: 1. Using Li-based crystals, they have a wide transparent range and a high laser damage threshold, and can achieve high optical gain; 2. Except for the LISe crystal which requires a ~2 μm laser pump, the other crystals can be pumped with commercially mature ~1 μm lasers; 3. By applying different optical parametric amplification conditions, mid-infrared laser pulse amplification in the wavelength range from ~1.15 μm to ~10 μm can be achieved; 4. Broadband pulse signal amplification can be obtained, and the typical signal light gain bandwidth is 30 nm - 400 nm (~1 μm pump) and 400 nm – 3 μm (~2 μm pump). Description of the Drawings

[0008] Figure 1 It is a 3D contour map of the relationship between the non-collinear angle and the wavelengths of the pump light and the signal light under type-I non-collinear optical parametric amplification for four crystals. Different grayscales represent different non-collinear angles. The non-white areas provide broadband optical parametric amplification, and the maximum non-collinear angle corresponds to ultra-broadband optical parametric amplification.

[0009] Figure 2 It is the signal light gain spectrum corresponding to the Li-based crystal under ultra-broadband optical parametric amplification conditions calculated at pump wavelengths of 1.03 μm, 1.064 μm, 1.94 μm, and 2.1 μm. Among them, the pump light intensity is uniformly set to 10 GW / cm 2 , and the crystal length is set according to the condition of obtaining the same maximum gain value G = 1000. Under the pumping of a ~1 μm laser light source, the maximum signal light gain bandwidth reaches about 400 nm. Under the pumping of a ~2 μm laser light source, the maximum signal light gain bandwidth can reach about 3 μm. This bandwidth is sufficient to amplify the supercontinuum pulse and compress its pulse width to one optical cycle. Figure 2 Only the results of the signal light gain bandwidth are given. The wider the signal light gain bandwidth, the wider the corresponding idler light gain bandwidth. Specific implementation mode

[0010] Step 1: Select LGS, LGSe, LIS, and LISe as the crystals for optical parametric amplification, with o s +o i →e p as the optical parametric amplification category. According to and the high light transmittance range of the crystal, calculate the 3D contour map of the relationship between the non-collinear angle and the wavelengths of the pump light and the signal light when the pump light wave is in the ranges of 0.8 - 2.2 μm (LGS), 0.88 - 2.2 μm (LGSe), 1 - 2.2 μm (LIS), and 1.1 - 2.2 μm (LISe) respectively;

[0011] Step 2: According to the calculation results of Step 1, determine that the crystal combinations for achieving broadband optical parametric amplification under the pumping of commercial lasers at 1.03 μm, 1.064 μm, 1.94 μm, and 2.1 μm are LGS (pumped with wavelengths of 1.03 and 1.064 μm), LGSe (pumped with wavelengths of 1.03, 1.064, and 1.94 μm), LIS (pumped with wavelengths of 1.03 and 1.064 μm), and LISe (pumped with wavelengths of 1.94 and 2.1 μm);

[0012] Step 3: According to the results of Step 1 and Step 2, calculate the central signal light wavelength, idler light wavelength, non-collinear and phase matching angle parameters for achieving broadband and ultra-broadband optical parametric amplification according to ;

[0013] Specific amplification schemes are as follows Figure 1 as shown

[0014] For the LGS crystal: Using a 1.03 μm wavelength laser as the pump source, with a non-collinear angle of 0 - 2.75°, broadband optical amplification is performed on the signal light with a central wavelength in the range of 1.185 - 2.06 μm, and the corresponding idler light amplification range is 7.88 - 2.06 μm. Ultra-broadband optical amplification is obtained under the condition of α = 2.75° (λ s = 1.58 μm, λ i = 2.96 μm, θ = 38.24°); or using a 1.064 μm wavelength laser as the pump source, with a non-collinear angle of 0 - 2.62°, broadband optical amplification is performed on the signal light with a central wavelength in the range of 1.24 - 2.128 μm, and the corresponding idler light amplification range is 7.496 - 2.128 μm. Ultra-broadband optical amplification is obtained under the condition of α = 2.62° (λ s = 1.62 μm, λ i = 3.10 μm, θ = 40.12°);

[0015] For the LGSe crystal: Using a 1.03 μm wavelength laser as the pump source, with a non-collinear angle of 0 - 3.4°, broadband optical amplification is performed on the signal light with a central wavelength in the range of 1.138 - 2.06 μm, and the corresponding idler light amplification range is 10.853 - 2.06 μm. Ultra-broadband optical amplification is obtained under the condition of α = 3.4° (λ s = 1.56 μm, λ i = 3.03 μm, θ = 30.52°); or using a 1.064 μm wavelength laser as the pump source, with a non-collinear angle of 0 - 3.3°, broadband optical amplification is performed on the signal light with a central wavelength in the range of 1.182 - 2.128 μm, and the corresponding idler light amplification range is 10.658 - 2.128 μm. Ultra-broadband optical amplification is obtained under the condition of α = 3.3° (λ s = 1.61 μm, λ i = 3.13 μm, θ = 33.21°); or using a 1.94 μm wavelength laser as the pump source, with a non-collinear angle of 0 - 0.17°, broadband optical amplification is performed on the signal light with a central wavelength in the range of 3.48 - 3.88 μm, and the corresponding idler light amplification range is 4.384 - 3.88 μm. Ultra-broadband optical amplification is obtained under the condition of α = 0.17° (λ s = 3.65 μm, λ i = 4.14 μm, θ = 56.25°);

[0016] For the LIS crystal: Using a laser with a wavelength of 1.03 μm as the pump source, with a non-collinear angle of 0 - 3.1°, broadband optical amplification is performed on the signal light with a central wavelength in the range of 1.15 - 2.06 μm. The corresponding idler light amplification range is 9.66 - 2.06 μm, and an ultra-broadband optical amplification is obtained under the condition of α = 3.1° (λ s = 1.56 μm, λ i = 3.03 μm, θ = 19.24°); or using a laser with a wavelength of 1.064 μm as the pump source, with a non-collinear angle of 0 - 2.95°, broadband optical amplification is performed on the signal light with a central wavelength in the range of 1.205 - 2.128 μm. The corresponding idler light amplification range is 9.093 - 2.128 μm, and an ultra-broadband optical amplification is obtained under the condition of α = 2.95° (λ s = 1.62 μm, λ i = 3.10 μm, θ = 22.86°).

[0017] For the LISe crystal: Using a laser with a wavelength of 1.94 μm as the pump source, with a non-collinear angle of 0 - 1.35°, broadband optical amplification is performed on the signal light with a central wavelength in the range of 2.6 - 3.88 μm. The corresponding idler light amplification range is 7.72 - 3.88 μm, and an ultra-broadband optical amplification is obtained under the condition of α = 1.35° (λ s = 3.13 μm, λ i = 5.10 μm, θ = 48.63°); or using a laser with a wavelength of 2.1 μm as the pump source, with a non-collinear angle of 0 - 0.9°, broadband optical amplification is performed on the signal light with a central wavelength in the range of 3.04 - 4.2 μm. The corresponding idler light amplification range is 6.8 - 4.2 μm, and an ultra-broadband optical amplification is obtained under the condition of α = 0.9° (λ s = 3.52 μm, λ i = 5.21 μm, θ = 50.32°).

Claims

1. A design method for broadband mid-infrared laser pulses based on non-collinear optical parametric amplification technology, characterized in that, using a Li-based non-oxide crystal under specific type-I optical parametric amplification conditions to achieve broadband pulsed laser amplification, and the specific steps include: Step 1: Select LGS, LGSe, LIS or LISe as the optical parametric amplification crystal, with o s +o i →e p as the optical parametric amplification type. According to and the high light transmittance range of the crystal, calculate the 3D contour maps of the relationship between the non-collinear angle and the wavelengths of the pump light and the signal light for LGS in the pump light wave range of 0.8 - 2.2 μm, LGSe in the pump light wave range of 0.88 - 2.2 μm, LIS in the pump light wave range of 1 - 2.2 μm, and LISe in the pump light wave range of 1.1 - 2.2 μm; in the formula, v gs and v gi are the group velocities of the signal light and the idler light respectively; λ s and λ i are the wavelengths of the signal light and the idler light respectively; n s and n i are the refractive indices of the signal light and the idler light respectively, and α is the non-collinear angle, representing the angle between the signal wave vector and the pump wave vector; Step 2: According to the calculation results of Step 1, determine that the crystal combinations for achieving broadband optical parametric amplification under the pumping of commercial lasers at 1.03 μm, 1.064 μm, 1.94 μm, and 2.1 μm respectively are: LGS is selected when pumped at 1.03 and 1.064 μm wavelengths; LGSe is selected when pumped at 1.03, 1.064, and 1.94 μm wavelengths; LISe is selected when pumped at 1.03 and 1.064 μm wavelengths; LISe is selected when pumped at 1.94 and 2.1 μm wavelengths; Step 3: According to the results of Step 1 and Step 2, based on design and implement the central signal optical wavelength, idler optical wavelength, non-collinear and phase matching angle parameters for broadband and ultra-wideband optical parametric amplification; in the formula, θ is the phase matching angle, representing the angle between the pump wave vector and the optical axis, λ p is the pump wavelength, n op and n ep are the refractive indices of the o-ray and e-ray of the pump light.

2. The method according to claim 1, characterized in that the specific amplification scheme is: For the LGS crystal: Using a 1.03 μm wavelength laser as the pump source and a non-collinear angle of 0 - 2.75°, broadband optical amplification is performed on the signal light with a central wavelength in the range of 1.185 - 2.06 μm, and the corresponding idler light amplification range is 7.88 - 2.06 μm. Ultra-wideband optical amplification is achieved under the conditions of α = 2.75°, λ s = 1.58 μm, λ i = 2.96 μm, θ = 38.24°; or using a 1.064 μm wavelength laser as the pump source and a non-collinear angle of 0 - 2.62°, broadband optical amplification is performed on the signal light with a central wavelength in the range of 1.24 - 2.128 μm, and the corresponding idler light amplification range is 7.496 - 2.128 μm. Ultra-wideband optical amplification is achieved under the conditions of α = 2.62°, λ s = 1.62 μm, λ i = 3.10 μm, θ = 40.12°; For the LGSe crystal: Using a 1.03 μm wavelength laser as the pump source and a non-collinear angle of 0 - 3.4°, broadband optical amplification is performed on the signal light with a central wavelength in the range of 1.138 - 2.06 μm, and the corresponding idler light amplification range is 10.853 - 2.06 μm. Ultra-broadband optical amplification is obtained under the conditions of α = 3.4°, λ s = 1.56 μm, λ i = 3.03 μm, θ = 30.52°; or using a 1.064 μm wavelength laser as the pump source and a non-collinear angle of 0 - 3.3°, broadband optical amplification is performed on the signal light with a central wavelength in the range of 1.182 - 2.128 μm, and the corresponding idler light amplification range is 10.658 - 2.128 μm. Ultra-broadband optical amplification is obtained under the conditions of α = 3.3°, λ s = 1.61 μm, λ i = 3.13 μm, θ = 33.21°; or using a 1.94 μm wavelength laser as the pump source and a non-collinear angle of 0 - 0.17°, broadband optical amplification is performed on the signal light with a central wavelength in the range of 3.48 - 3.88 μm, and the corresponding idler light amplification range is 4.384 - 3.88 μm. Ultra-broadband optical amplification is obtained under the conditions of α = 0.17°, λ s = 3.65 μm, λ i = 4.14 μm, θ = 56.25°; For the LIS crystal: Using a 1.03-μm wavelength laser as the pump source and a non-collinear angle of 0 - 3.1°, broadband optical amplification is performed on the signal light with a central wavelength in the range of 1.15 - 2.06 μm, and the corresponding idler light amplification range is 9.66 - 2.06 μm. Ultra-wideband optical amplification is obtained under the conditions of α = 3.1°, λ s = 1.56 μm, λ i = 3.03 μm, θ = 19.24°; or using a 1.064-μm wavelength laser as the pump source and a non-collinear angle of 0 - 2.95°, broadband optical amplification is performed on the signal light with a central wavelength in the range of 1.205 - 2.128 μm, and the corresponding idler light amplification range is 9.093 - 2.128 μm. Ultra-wideband optical amplification is obtained under the conditions of α = 2.95°, λ s = 1.62 μm, λ i = 3.10 μm, θ = 22.86°; For LISe crystals: Using a 1.94-μm wavelength laser as the pump source, with a non-collinear angle ranging from 0 to 1.35°, broadband optical amplification is performed on the signal light with a central wavelength in the range of 2.6 - 3.88 μm. The corresponding idler light amplification range is 7.72 - 3.88 μm, and ultra-broadband optical amplification is achieved under the conditions of α = 1.35°, λ s = 3.13 μm, λ i = 5.10 μm, θ = 48.63°; or using a 2.1-μm wavelength laser as the pump source, with a non-collinear angle ranging from 0 to 0.9°, broadband optical amplification is respectively performed on the signal light with a central wavelength in the range of 3.04 - 4.2 μm. The corresponding idler light amplification range is 6.8 - 4.2 μm, and ultra-broadband optical amplification is achieved under the conditions of α = 0.9°, λ s = 3.52 μm, λ i = 5.21 μm, θ = 50.32°.

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