Terahertz parametric source generation device based on pulse seed injection

Abstract

The invention provides a terahertz parametric source generation device based on pulse seed injection, which can be applied to the technical field of solid laser and nonlinear optical frequency conversion. The device comprises a laser synchronization unit which is used for carrying out light splitting on initial nanosecond pulse laser with the pulse width of nanosecond magnitude to obtain reflected nanosecond pulse laser and transmitted nanosecond pulse laser; the pumping laser generating unit is used for generating subnanosecond pulse pumping laser with the pulse width of subnanosecond magnitude according to the reflected nanosecond pulse laser and the auxiliary drifting effect; the seed laser source generation unit is used for carrying out wavelength adjustment on the transmission nanosecond pulse laser to obtain nanosecond pulse seed laser with nanosecond pulse width; and the terahertz parameter generation unit comprises a nonlinear optical crystal and is used for generating terahertz waves under the common irradiation of the subnanosecond pulse pumping laser and the nanosecond pulse seed laser so as to generate a terahertz parameter source.

Description

Technical Field

[0001] The present disclosure relates to the technical field of solid-state laser and nonlinear optical frequency conversion, and more specifically, to a terahertz parameter source generation device based on pulse seed injection. Background Art

[0002] Terahertz parametric sources based on stimulated electromagnetic coupler scattering effect are an important means to generate high-power, widely tunable terahertz waves. Among them, common terahertz parametric source technologies include terahertz parametric generation (TPG), terahertz parametric oscillation (TPO) and injection-seeded terahertz parametric generation (is-TPG).

[0003] TPG directly uses pump laser to pump nonlinear optical crystal. Although it can generate terahertz waves at the dominant frequency, the output power is low and frequency tuning cannot be achieved. TPO uses a cavity structure to achieve resonant amplification of Stokes light in the cavity, thereby improving the conversion efficiency of terahertz waves. However, due to the strong absorption and low gain close to the vibration mode frequency point, the output power and tuning bandwidth are limited. is-TPG uses a seed laser with the same wavelength as the Stokes light, and simultaneously injects the nonlinear optical crystal with the pump laser at a non-collinear phase matching angle, causing strong Stokes light parametric amplification, thereby generating high-power terahertz waves, and by tuning the seed laser wavelength and non-collinear phase matching angle, the terahertz tuning bandwidth can be expanded. However, in the terahertz parameter process of is-TPG, the stimulated Brillouin scattering (SBS) effect will participate in consuming the pump laser without generating terahertz photons, especially for pump lasers with wider pulse widths, the SBS effect is more serious.

[0004] Therefore, how to generate a terahertz parametric source with ultra-wideband tuning, high average power, high peak power and good pulse sequence stability has become a technical problem that needs to be solved urgently. Summary of the invention

[0005] In view of this, the present disclosure provides a terahertz parameter source generation device based on pulse seed injection.

[0006] The present disclosure provides a terahertz parameter source generation device based on pulse seed injection, comprising: a laser synchronization unit 100, used for splitting an initial nanosecond pulse laser with a pulse width of the nanosecond order to obtain a reflected nanosecond pulse laser and a transmitted nanosecond pulse laser; a pump laser generation unit 200, used for generating a sub-nanosecond pulse pump laser with a pulse width of the sub-nanosecond order according to the reflected nanosecond pulse laser and an auxiliary drift effect; a seed laser source generation unit 300, used for adjusting the wavelength of the transmitted nanosecond pulse laser to obtain a nanosecond pulse seed laser with a pulse width of the nanosecond order; a terahertz parameter generation unit 400, comprising: a nonlinear optical crystal 401, used for generating a terahertz wave under the common irradiation of the sub-nanosecond pulse pump laser and the nanosecond pulse seed laser, thereby generating a terahertz parameter source.

[0007] According to an embodiment of the present disclosure, the laser synchronization unit 100 includes: a nanosecond pulse laser 101 for generating the initial nanosecond pulse laser; a laser spectrometer 102 for splitting the initial nanosecond pulse laser to obtain the reflected nanosecond pulse laser and the transmitted nanosecond pulse laser.

[0008] According to an embodiment of the present disclosure, the pump laser generating unit 200 includes: a sub-nanosecond pulse laser master oscillator 201, which is used to generate a first sub-nanosecond pulse laser with a pulse width of the sub-nanosecond order according to the reflected nanosecond pulse laser and the auxiliary drift effect; a sub-nanosecond pulse laser amplifier 202, which is used to amplify the power of the first sub-nanosecond pulse laser to obtain a second sub-nanosecond pulse laser; a sub-nanosecond laser frequency multiplier 203, which is used to adjust the frequency of the second sub-nanosecond pulse laser to obtain a third sub-nanosecond pulse laser; and a sub-nanosecond laser polarization controller 204, which is used to modulate the polarization state of the third sub-nanosecond pulse laser to obtain a sub-nanosecond pulse pump laser with a polarization state of vertical polarization.

[0009] According to an embodiment of the present disclosure, the emission wavelengths of the laser crystals respectively included in the above-mentioned sub-nanosecond pulse laser master oscillator 201, the above-mentioned sub-nanosecond pulse laser amplifier 202 and the above-mentioned nanosecond pulse laser 101 are consistent; the pump timings of the pump sources respectively corresponding to the above-mentioned sub-nanosecond pulse laser master oscillator 201, the above-mentioned sub-nanosecond pulse laser amplifier 202 and the above-mentioned nanosecond pulse laser 101 are synchronized; the above-mentioned sub-nanosecond pulse laser master oscillator 201 also includes: a saturable absorber for receiving the above-mentioned reflected nanosecond pulse laser, and based on the auxiliary drift effect, controlling the synchronization of the above-mentioned reflected nanosecond pulse laser and the above-mentioned first sub-nanosecond pulse laser.

[0010] According to an embodiment of the present disclosure, the terahertz parameter generation unit 400 further includes: a pump laser reflector 402, used to reflect the sub-nanosecond pulse pump laser so as to reflect the sub-nanosecond pulse pump laser to a preset position of the nonlinear optical crystal 401; and a seed laser reflector 403, used to reflect the nanosecond pulse seed laser so as to reflect the nanosecond pulse seed laser to the preset position of the nonlinear optical crystal 401.

[0011] According to an embodiment of the present disclosure, the pump laser reflector 402 and the seed laser reflector 403 are respectively mounted on corresponding electrically-controlled turntables, wherein the electrically-controlled turntables are used to adjust the emission angles of the lasers reflected by the pump laser reflector 402 and the seed laser reflector 403; two electrically-controlled turntables corresponding to the pump laser reflector 402 and the seed laser reflector 403 are respectively mounted on corresponding electrically-controlled displacement platforms, wherein the electrically-controlled displacement platforms are used to translate the lasers reflected by the pump laser reflector 402 and the seed laser reflector 403 in a horizontal direction; wherein the two laser beams reflected by the pump laser reflector 402 and the seed laser reflector 403 intersect at a non-collinear angle of 0.5° to 7° around the preset position.

[0012] According to an embodiment of the present disclosure, the seed laser source generating unit 300 includes: a nonlinear optical frequency converter 301, which is used to adjust the wavelength of the transmitted nanosecond pulse laser to obtain a first nanosecond pulse seed laser with a wavelength within a preset wavelength range and a pulse width of the nanosecond order; a nanosecond laser frequency doubler 302, which is used to adjust the frequency of the first nanosecond pulse seed laser to obtain a second nanosecond pulse seed laser; and a nanosecond laser polarization controller 303, which is used to modulate the polarization state of the second nanosecond pulse seed laser to obtain a nanosecond pulse seed laser with a vertical polarization state.

[0013] According to an embodiment of the present disclosure, the sub-nanosecond pulse laser master oscillator 201 includes a microcavity structure with bonded crystal Nd:YAG+Cr:YAG as the laser crystal; the sub-nanosecond pulse laser amplifier 202 includes a traveling wave amplification structure with bonded crystal YAG+Nd:YAG as the laser crystal; the sub-nanosecond laser frequency doubler 203 and the nanosecond laser frequency doubler 302 both include a half-wave plate of a first preset wavelength; the sub-nanosecond laser frequency doubler 203 adopts a constant temperature design, and the nanosecond laser frequency doubler 302 adopts a variable temperature design; the sub-nanosecond laser polarization controller 204 and the nanosecond laser polarization controller 303 both include a half-wave plate of a first preset wavelength and a second preset wavelength, wherein the half-wave plates of the first preset wavelength and the second preset wavelength are switched accordingly according to the wavelength of the laser incident to the sub-nanosecond laser polarization controller 204 and the nanosecond laser polarization controller 303.

[0014] According to an embodiment of the present disclosure, the nonlinear optical crystal 401 includes one of the following: magnesium oxide doped lithium niobate and potassium titanyl phosphate; the nonlinear optical crystal 401 is designed as an isosceles trapezoidal block; the subnanosecond pulse pump laser and the nanosecond pulse seed laser are incident from one waist face of the isosceles trapezoidal block, intersect at the bottom face of the isosceles trapezoidal block, and are totally reflected from the bottom face of the isosceles trapezoidal block before being emitted from another waist face of the isosceles trapezoidal block; based on the joint irradiation of the subnanosecond pulse pump laser and the nanosecond pulse seed laser, the terahertz wave generated by the nonlinear optical crystal 401 is perpendicular to the bottom surface of the isosceles trapezoidal block and is emitted from the bottom surface of the isosceles trapezoidal block; the nonlinear optical crystal 401 is installed on a height-adjustable lifting platform, wherein the lifting platform is used to adjust the nonlinear optical crystal 401 of a preset material to a corresponding preset height.

[0015] According to an embodiment of the present disclosure, the frequency range of the terahertz wave includes 0.5 Hz-13.6 THz.

[0016] According to the pulse seed injection-based terahertz parameter source generation device provided by the embodiment of the present disclosure, after the initial nanosecond pulse laser with a pulse width of the nanosecond order is split by a laser synchronization unit to obtain a reflected nanosecond pulse laser and a transmitted nanosecond pulse laser, a sub-nanosecond pulse pump laser with a pulse width of the sub-nanosecond order is generated by using the reflected nanosecond pulse laser and the auxiliary drift effect, the wavelength of the transmitted nanosecond pulse laser is adjusted by a seed laser source generation unit to obtain a nanosecond pulse seed laser with a pulse width of the nanosecond order, and then the nonlinear optical crystal included in the terahertz parameter generation unit is used to generate a sub-nanosecond pulse pump laser with a pulse width of the sub-nanosecond order. The invention relates to a technical means for generating terahertz waves and then generating a terahertz parametric source under the joint irradiation of a subnanosecond pulse pump laser and a nanosecond pulse seed laser. The terahertz parametric source pumped by a subnanosecond or picosecond pulse laser has a significant inhibitory effect on the SBS effect, and the pump laser is mainly used for the stimulated Raman scattering process, thereby improving the conversion efficiency of the terahertz wave. In addition, the subnanosecond or picosecond pulse laser has a high peak power, which is beneficial to the forward progress of the nonlinear optical process, thereby obtaining a terahertz parametric source with the advantages of ultra-wideband tuning, high average power, high peak power and good pulse sequence stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0018] Figure 1 A schematic diagram of the structure of a terahertz parameter source generation device based on pulse seed injection according to an embodiment of the present disclosure is shown; and

[0019] Figure 2 A schematic diagram schematically shows the frequency range of terahertz waves generated by a terahertz parameter source generation device based on a pulse seed injection type according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0020] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0021] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0022] All terms used herein, including technical and scientific terms, have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification, and should not be interpreted in an idealized or overly rigid manner.

[0023] When using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted as the meaning of the expression generally understood by those skilled in the art. For example, "a system having at least one of A, B, and C" should include but not be limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc. When using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted as the meaning of the expression generally understood by those skilled in the art. For example, "a system having at least one of A, B, or C" should include but not be limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.

[0024] It should also be noted that the directional terms mentioned in the embodiments, such as "upper", "lower", "front", "back", "left", "right", etc., are only reference directions of the drawings and are not intended to limit the scope of protection of the present disclosure. Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or configurations will be omitted when they may cause confusion in the understanding of the present disclosure.

[0025] Seed injection terahertz parametric generation includes continuous seed injection terahertz parametric generation and pulse seed injection terahertz parametric generation (ips-TPG). Since pulse seeds have higher peak power, it is easier to achieve coherent stimulated electromagnetic coupler scattering in a broadband range, thereby greatly improving the terahertz wave output power and expanding the terahertz tuning bandwidth.

[0026] Therefore, the embodiments of the present disclosure improve the pulse seed injection type terahertz parameter generation method to solve the technical problem of how to generate a terahertz parameter source with ultra-wideband tuning, high average power, high peak power and good pulse sequence stability.

[0027] Figure 1 The schematic diagram shows the structure of a terahertz parameter source generation device based on pulse seed injection according to an embodiment of the present disclosure.

[0028] like Figure 1As shown, the terahertz parameter source generation device based on pulse seed injection may include: a laser synchronization unit 100 , a pump laser generation unit 200 , a seed laser source generation unit 300 and a terahertz parameter generation unit 400 .

[0029] The laser synchronization unit 100 can be used to split the initial nanosecond pulse laser with a pulse width of nanosecond order to obtain reflected nanosecond pulse laser and transmitted nanosecond pulse laser.

[0030] For example, the initial nanosecond pulse laser, the reflected nanosecond pulse laser, and the transmitted nanosecond pulse laser can all be 1064 nm fundamental frequency lasers.

[0031] The pump laser generating unit 200 can be used to generate a sub-nanosecond pulse pump laser with a pulse width of the sub-nanosecond order according to the reflected nanosecond pulse laser and the auxiliary drift effect.

[0032] For example, the sub-nanosecond pulsed pump laser may be a 1064 nm fundamental frequency laser or a 532 nm frequency-doubled frequency laser.

[0033] According to an embodiment of the present disclosure, by utilizing the pump laser generating unit 200 to generate a sub-nanosecond pulse pump laser with a pulse width of the sub-nanosecond order based on the reflected nanosecond pulse laser and the auxiliary drift effect, the auxiliary drift effect can be utilized to achieve synchronization between sub-nanosecond and nanosecond pulse lasers, and the jitter of the sub-nanosecond pulse sequence can be compressed from the microsecond order to the hundreds of picosecond order.

[0034] The seed laser source generating unit 300 can be used to adjust the wavelength of the transmitted nanosecond pulse laser to obtain a nanosecond pulse seed laser with a pulse width of the nanosecond order.

[0035] For example, the nanosecond pulse seed laser may be a fundamental frequency laser with a wavelength in the range of 1066 nm to 1092 nm or a frequency-doubled laser with a wavelength in the range of 533 nm to 546 nm.

[0036] The terahertz parameter generation unit 400 includes a nonlinear optical crystal 401. The nonlinear optical crystal 401 can be used to generate terahertz waves under the joint irradiation of a sub-nanosecond pulse pump laser and a nanosecond pulse seed laser, thereby generating a terahertz parameter source.

[0037] According to the embodiment of the present disclosure, after the initial nanosecond pulse laser with a pulse width of the nanosecond order is split by a laser synchronization unit to obtain a reflected nanosecond pulse laser and a transmitted nanosecond pulse laser, a subnanosecond pulse pump laser with a pulse width of the subnanosecond order is generated by using the reflected nanosecond pulse laser and the auxiliary drift effect, and the wavelength of the transmitted nanosecond pulse laser is adjusted by a seed laser source generation unit to obtain a nanosecond pulse seed laser with a pulse width of the nanosecond order, and then the nonlinear optical crystal included in the terahertz parameter generation unit is used to generate a subnanosecond pulse pump laser. A technical means of generating terahertz waves and then generating terahertz parametric sources under the joint irradiation of a nanosecond pulse seed laser. Since the terahertz parametric source pumped by a subnanosecond or picosecond pulse laser has a significant inhibitory effect on the SBS effect, and the pump laser is mainly used for the stimulated Raman scattering process, the conversion efficiency of the terahertz wave is improved. In addition, the subnanosecond or picosecond pulse laser has a high peak power, which is beneficial to the forward progress of the nonlinear optical process, thereby obtaining a terahertz parametric source with the advantages of ultra-wideband tuning, high average power, high peak power and good pulse sequence stability.

[0038] exist Figure 1 In the embodiment, the laser synchronization unit 100 may include: a nanosecond pulse laser 101 and a laser beam splitter 102 .

[0039] The nanosecond pulse laser 101 can be used to generate an initial nanosecond pulse laser. The laser beam splitter 102 can be used to split the initial nanosecond pulse laser to obtain a reflected nanosecond pulse laser and a transmitted nanosecond pulse laser. For example, the nanosecond pulse laser 101 is an electro-optical Q-switched laser.

[0040] like Figure 1 As shown, the pump laser generating unit 200 may include: a sub-nanosecond pulse laser master oscillator 201 , a sub-nanosecond pulse laser amplifier 202 , a sub-nanosecond laser frequency doubler 203 and a sub-nanosecond laser polarization controller 204 .

[0041] The sub-nanosecond pulse laser master oscillator 201 can be used to generate a first sub-nanosecond pulse laser with a pulse width of the sub-nanosecond order according to the reflected nanosecond pulse laser and the auxiliary drift effect. The sub-nanosecond pulse laser amplifier 202 can be used to amplify the power of the first sub-nanosecond pulse laser to obtain a second sub-nanosecond pulse laser. The sub-nanosecond laser frequency multiplier 203 can be used to adjust the frequency of the second sub-nanosecond pulse laser to obtain a third sub-nanosecond pulse laser. The sub-nanosecond laser polarization controller 204 can be used to modulate the polarization state of the third sub-nanosecond pulse laser to obtain a sub-nanosecond pulse pump laser with a polarization state of vertical polarization.

[0042] Figure 1The laser crystals included in the sub-nanosecond pulse laser master oscillator 201, the sub-nanosecond pulse laser amplifier 202 and the nanosecond pulse laser 101 have the same emission wavelength. For example, the sub-nanosecond pulse laser master oscillator 201, the sub-nanosecond pulse laser amplifier 202 and the nanosecond pulse laser 101 all use laser crystals with the same emission wavelength (1064nm fundamental frequency).

[0043] exist Figure 1 In the embodiment, the pump timing of the pump source corresponding to each of the sub-nanosecond pulse laser master oscillator 201, the sub-nanosecond pulse laser amplifier 202 and the nanosecond pulse laser 101 is synchronized. For example, the sub-nanosecond pulse laser master oscillator 201, the sub-nanosecond pulse laser amplifier 202 and the nanosecond pulse laser 101 all use a synchronous pumping signal setting to achieve the pump timing synchronization of the pump source corresponding to each of them. For example, a signal generator can be used to synchronize the pump timing of the semiconductor pump source in the sub-nanosecond pulse laser master oscillator 201, the sub-nanosecond pulse laser amplifier 202 and the nanosecond pulse laser 101.

[0044] Figure 1 The sub-nanosecond pulse laser master oscillator 201 may also include: a saturable absorber for receiving the reflected nanosecond pulse laser, and controlling the synchronization of the reflected nanosecond pulse laser and the first sub-nanosecond pulse laser based on the auxiliary drift effect. At this time, the reflected nanosecond pulse laser, the first sub-nanosecond pulse laser and the transmitted nanosecond pulse laser are synchronized. The reflected nanosecond pulse laser, the first sub-nanosecond pulse laser, the second sub-nanosecond pulse laser, the third sub-nanosecond pulse laser, the sub-nanosecond pulse pump laser and the transmitted nanosecond pulse laser are all synchronized.

[0045] For example, the initial nanosecond pulse laser emitted by the nanosecond pulse laser 101 can be reflected and irradiated at a low power (hundreds of mW) to the saturable absorber of the sub-nanosecond pulse laser master oscillator 201 through the laser spectrometer 102, and the auxiliary drift effect can be used to achieve synchronization between sub-nanosecond and nanosecond pulse lasers, and compress the jitter of the sub-nanosecond pulse sequence from the microsecond level to the hundred picosecond level.

[0046] The first sub-nanosecond pulse laser emitted by the sub-nanosecond pulse laser master oscillator 201 is amplified by the sub-nanosecond pulse laser amplifier 202, and then a 532nm frequency-doubled laser is obtained after passing through the sub-nanosecond laser frequency doubler 203. Among them, the sub-nanosecond laser frequency doubler 203 has a switching function, and can output a 1064nm base frequency or a 532nm frequency-doubled laser according to demand. That is, the third sub-nanosecond pulse laser obtained by the sub-nanosecond laser frequency doubler 203 can include one of the following: a 1064nm base frequency and a 532nm frequency-doubled laser. The third sub-nanosecond pulse laser output by the sub-nanosecond laser frequency doubler 203 passes through the sub-nanosecond laser polarization controller 204, and the polarization state of the third sub-nanosecond pulse laser is modulated to vertical polarization. The sub-nanosecond laser polarization controller 204 outputs the obtained sub-nanosecond pulse pump laser to the pump laser reflector 402.

[0047] Figure 1 The sub-nanosecond pulse laser master oscillator 201 in the invention may include a micro-cavity structure with bonded crystal Nd:YAG+Cr:YAG as the laser crystal. One end of the cavity is coated with a 808nm high-transmittance and 1064nm high-reflection film, and the other end is coated with a 808nm high-transmittance and 1064nm partial transmission film (transmittance T=50%). The cavity length is 5-10mm, and the corresponding output laser pulse width is in the sub-nanosecond order. The micro-cavity structure is pumped by a 808nm central wavelength laser emitted by a semiconductor pump source, and its pulse repetition frequency is 500Hz-5kHz. The sub-nanosecond pulse laser master oscillator 201 generates pulsed laser based on the passive Q-switching principle.

[0048] The sub-nanosecond pulse laser amplifier 202 may include a traveling wave amplification structure using bonded crystal YAG+Nd:YAG as a laser crystal. For example, the sub-nanosecond pulse laser amplifier 202 may adopt an end-pumping structure using bonded crystal YAG+Nd:YAG as an amplifying crystal, with both ends of the bonded crystal plated with 808nm and 1064nm high-transmittance films, and pumped by a 808nm central wavelength laser emitted by a semiconductor pump source, and its pumping timing is synchronized with the semiconductor pump source in the sub-nanosecond pulse laser master oscillator 201 through a signal generator.

[0049] The master oscillator seed laser (i.e., the first sub-nanosecond pulse laser) is input into the end-pumped sub-nanosecond pulse laser amplifier 202, and a signal generator is used to synchronize the pump pulse timing of the semiconductor pump source in the sub-nanosecond pulse laser master oscillator 201 and the sub-nanosecond pulse laser amplifier 202, so as to achieve high-power sub-nanosecond pulse laser output.

[0050] like Figure 1 As shown, the seed laser source generating unit 300 may include: a nonlinear optical frequency converter 301 , a nanosecond laser frequency doubler 302 , and a nanosecond laser polarization controller 303 .

[0051] The nonlinear optical frequency converter 301 can be used to adjust the wavelength of the transmitted nanosecond pulse laser to obtain a first nanosecond pulse seed laser with a wavelength within a preset wavelength range and a pulse width of the nanosecond order. The nanosecond laser frequency doubler 302 can be used to adjust the frequency of the first nanosecond pulse seed laser to obtain a second nanosecond pulse seed laser. The nanosecond laser polarization controller 303 can be used to modulate the polarization state of the second nanosecond pulse seed laser to obtain a nanosecond pulse seed laser with a vertical polarization state. For example, the preset wavelength range can be 1066nm-1092nm.

[0052] For example, the initial nanosecond pulse laser (1064nm fundamental frequency laser) emitted by the nanosecond pulse laser 101 is transmitted through the laser beam splitter 102 and incident on the nonlinear optical frequency converter 301 to convert the 1064nm fundamental frequency laser into a continuously adjustable fundamental frequency seed laser (i.e., the first nanosecond pulse seed laser) in the wavelength range of 1066nm-1092nm. The first nanosecond pulse seed laser is frequency-adjusted by the nanosecond laser frequency doubler 302 to obtain a wavelength-continuously adjustable doubled frequency seed laser (i.e., the second nanosecond pulse seed laser) in the wavelength range of 533nm-546nm. The nanosecond laser frequency doubler 302 has a switching function and can output a 1066nm-1092nm fundamental frequency or 533nm-546nm doubled frequency wavelength continuously adjustable seed laser according to demand. That is, the nanosecond pulse seed laser obtained by the nanosecond laser frequency doubler 302 may include one of the following: a fundamental frequency laser with a wavelength range of 1066nm-1092nm or a frequency doubled laser with a wavelength range of 533nm-546nm. The second nanosecond pulse seed laser output by the nanosecond laser frequency doubler 302 passes through the nanosecond laser polarization controller 303, and the polarization state of the second nanosecond pulse seed laser is modulated to vertical polarization. The nanosecond laser polarization controller 303 outputs the obtained nanosecond pulse seed laser to the seed laser reflector 403.

[0053] For example, the nonlinear optical frequency converter 301 can adopt a frequency doubler-optical parametric oscillator structure, with KTP (potassium titanyl phosphate, KTiOPO4) or LBO (LiB3O5 Lithium Triborate) as a nonlinear optical crystal, and convert the 1064nm fundamental frequency laser emitted by the nanosecond pulse laser 101 into a fundamental frequency seed laser (i.e., the first nanosecond pulse seed laser) with a wavelength range of 1066-1092nm and continuously adjustable wavelength through nonlinear optical frequency conversion.

[0054] The sub-nanosecond laser frequency doubler 203 and the nanosecond laser frequency doubler 302 may both include a half-wave plate of a first preset wavelength.

[0055] For example, the first preset wavelength may be 1064 nm.

[0056] The sub-nanosecond laser frequency doubler 203 adopts a constant temperature design, and the nanosecond laser frequency doubler 302 adopts a variable temperature design.

[0057] For example, the sub-nanosecond laser frequency doubler 203 and the nanosecond laser frequency doubler 302 may both use LBO as the nonlinear optical crystal, so that it has the characteristics of high damage threshold and temperature tunability.

[0058] For example, since the pump laser branch (pump laser generating unit 200) does not need a continuously adjustable wavelength function, the sub-nanosecond laser frequency doubler 203 can adopt a constant temperature design, and by tuning the 1064nm half-wave plate in the sub-nanosecond laser frequency doubler 203, it can output a 1064nm fundamental frequency or 532nm doubled frequency pump laser according to demand. Since the seed laser branch (seed laser source generating unit 300) requires a continuously adjustable wavelength function, the nanosecond laser frequency doubler 302 can adopt a variable temperature design, and the wavelength of the fundamental frequency seed laser with a continuously adjustable wavelength in the wavelength range of 1066nm-1092nm output by the nonlinear optical frequency converter 301 can be converted into a wavelength of the continuously adjustable wavelength doubled frequency seed laser in the wavelength range of 533nm-546nm through temperature tuning. Similarly, by adjusting the 1064nm half-wave plate in the nanosecond laser frequency doubler 302, it can output a wavelength range of 1066nm-1092nm fundamental frequency or 533nm-546nm doubled frequency seed laser according to demand.

[0059] The sub-nanosecond laser polarization controller 204 and the nanosecond laser polarization controller 303 both include half-wave plates of a first preset wavelength and a second preset wavelength, wherein the half-wave plates of the first preset wavelength and the second preset wavelength are switched accordingly according to the wavelength of the laser incident to the sub-nanosecond laser polarization controller 204 and the nanosecond laser polarization controller 303.

[0060] For example, the first preset wavelength may be 1064 nm, and the second preset wavelength may be 532 nm.

[0061] For example, the sub-nanosecond laser polarization controller 204 and the nanosecond laser polarization controller 303 can both adopt a switchable design of 1064nm and 532nm half-wave plates. When the terahertz source is pumped by a 1064nm laser, the laser polarization controller is switched to a 1064nm half-wave plate, and the polarization state of the 1064nm fundamental frequency band laser is modulated to a vertical polarization by rotating the 1064nm half-wave plate. When the terahertz source is pumped by a 532nm laser, the laser polarization controller is switched to a 532nm half-wave plate, and the polarization state of the 532nm frequency doubling band laser is modulated to a vertical polarization by rotating the 532nm half-wave plate.

[0062] exist Figure 1In the embodiment, the terahertz parameter generation unit 400 may further include: a pump laser reflection mirror 402 and a seed laser reflection mirror 403 .

[0063] The pump laser reflector 402 can be used to reflect the sub-nanosecond pulse pump laser to a preset position of the nonlinear optical crystal 401. The seed laser reflector 403 can be used to reflect the nanosecond pulse seed laser to a preset position of the nonlinear optical crystal 401.

[0064] For example, the pump laser reflector 402 and the seed laser reflector 403 can both use 45-degree high-reflection mirrors in the 1064nm and 532nm bands. The propagation directions of the pump laser and the seed laser are tuned by the pump laser reflector 402 and the seed laser reflector 403, respectively, and the two lasers can be transmitted to the exit surface of the nonlinear optical crystal 401 at a non-collinear phase matching angle and in a co-intersecting manner.

[0065] like Figure 1 As shown, the pump laser reflector 402 and the seed laser reflector 403 are respectively mounted on corresponding electric control turntables, wherein the electric control turntable is used to adjust the emission angle of the laser reflected by the pump laser reflector 402 and the seed laser reflector 403. The angle tuning of the laser in the horizontal direction can be achieved.

[0066] The two electrically controlled turntables corresponding to the pump laser reflector 402 and the seed laser reflector 403 are respectively installed on the corresponding electrically controlled displacement platforms, wherein the electrically controlled displacement platforms are used to translate the laser reflected by the pump laser reflector 402 and the seed laser reflector 403 in the horizontal direction, so as to realize the translation of the laser beam in space.

[0067] Figure 1 The two laser beams reflected by the pump laser reflecting mirror 402 and the seed laser reflecting mirror 403 intersect at a non-collinear angle of 0.5° to 7° around a preset position.

[0068] Figure 1 The two electrically-controlled turntables and the two electrically-controlled displacement platforms work together. By tuning the pump laser reflector 402 and the seed laser reflector 403, the pump laser and the seed laser can be transmitted to the nonlinear optical crystal 401 at a non-collinear phase matching angle around a fixed point in space. The two laser beams can be tuned at a non-collinear angle of 0.5° to 7° around a fixed point in space, thereby realizing non-collinear phase-matched pulse seed injection-type terahertz parameter generation.

[0069] Figure 1The nonlinear optical crystal 401 in the invention includes one of the following: magnesium oxide doped lithium niobate (MgO:LiNbO3) and potassium titanyl phosphate (KTP). The nonlinear optical crystal 401 can be designed as an isosceles trapezoidal block. The subnanosecond pulse pump laser and the nanosecond pulse seed laser are incident from one waist face of the isosceles trapezoidal block, intersect at the bottom face of the isosceles trapezoidal block, and are totally reflected by the bottom face of the isosceles trapezoidal block before being emitted from another waist face of the isosceles trapezoidal block. Based on the joint irradiation of the subnanosecond pulse pump laser and the nanosecond pulse seed laser, the nonlinear optical crystal 401 generates a terahertz wave perpendicular to the bottom surface of the isosceles trapezoidal block and is emitted from the bottom surface of the isosceles trapezoidal block. The nonlinear optical crystal 401 is installed on a height-adjustable lifting platform, wherein the lifting platform is used to adjust the nonlinear optical crystal 401 of the preset material to a corresponding preset height for the nonlinear optical crystal 401 of the preset material.

[0070] LiNbO3 crystal belongs to the trigonal system, negative uniaxial crystal, ilmenite structure, and is a ferroelectric crystal with a Curie temperature of about 1140℃ and good transmittance in the 0.4 to 5.5μm band. Magnesium oxide doped lithium niobate (MgO: LiNbO3) crystal has high resistance to light damage and photorefractive index, as well as mature growth process, and is widely used in laser devices, electro-optical modulation devices, optical waveguides, and nonlinear optical frequency conversion. KTP crystal belongs to the orthorhombic system, positive biaxial crystal, and is a ferroelectric crystal with good transmittance in the 0.35 to 4.5μm band. Its resistance to light damage is more than three times that of LiNbO3 crystal. In addition, many A1 transverse optical modes in KTP crystal are located in the terahertz band, and they are both infrared and Raman active, making it a very potential terahertz parametric gain medium. Stimulated electromagnetic coupler scattering based on KTP crystal can achieve terahertz radiation that almost covers the entire terahertz band.

[0071] For example, the nonlinear optical crystal 401 can be made of magnesium oxide doped lithium niobate and KTP nonlinear optical crystal, respectively realizing the terahertz wave output in the low frequency band and high frequency band of the terahertz. In order to meet the phase matching condition, the terahertz wave is emitted from the surface of the bottom surface of the isosceles trapezoidal block vertically, and the pump laser and the seed laser are both totally reflected on the surface of the nonlinear optical crystal 401, and the nonlinear optical crystal 401 can be designed with an isosceles trapezoidal block. For MgO:LiNbO3 and KTP nonlinear optical crystals 401, the trapezoidal bottom angles can be 65° and 60° respectively. The pump laser and the seed laser are incident from the waist surface of the trapezoidal block and intersect at the bottom surface of the trapezoidal block. The generated terahertz wave is emitted from the bottom surface of the crystal at a vertical angle. The crystal optical axis z-axis is along the thickness direction (vertical direction), that is, the polarization directions of the pump laser and the seed laser are along the crystal z-axis direction. At this time, the polarization direction of the terahertz wave generated by satisfying phase matching is also in the vertical direction. The nonlinear optical crystal 401 is installed on a height-adjustable lifting platform, which can realize the switching between MgO:LiNbO3 and KTP nonlinear optical crystal 401.

[0072] By tuning the wavelength of the seed laser output by the nonlinear optical frequency converter 301, and tuning the horizontal displacement and reflection angle of the pump laser reflector 402 and the seed laser reflector 403, pulse seed injection-type terahertz parameter generation of 1064nm and 532nm pumping can be achieved in the nonlinear optical crystal 401, thereby achieving 0.5-13.6THz ultra-wideband tunable high-power terahertz radiation.

[0073] Figure 2 A schematic diagram schematically shows the frequency range of terahertz waves generated by a terahertz parameter source generation device based on a pulse seed injection type according to an embodiment of the present disclosure.

[0074] like Figure 2 As shown, based on 1064nm laser pumping MgO:LiNbO3 nonlinear optical crystal 401, a low-frequency terahertz band of 0.5-4THz can be generated, and the maximum average power reaches the sub-milliwatt level. Based on 1064nm laser pumping KTP nonlinear optical crystal 401, a medium-frequency terahertz band of 3.0-6.0THz can be generated, and the maximum average power reaches the order of hundreds of microwatts. Based on 532nm laser pumping KTP nonlinear optical crystal 401, high-frequency terahertz bands of 5.0-6.2THz, 6.7-7.1THz, 7.3-7.9THz, 11.1-12.1THz and 13.0-13.6THz can be generated, and the maximum average power reaches the order of hundreds of microwatts. Thus, high-power terahertz radiation covering ultra-wideband tuning of 0.5-13.6THz is comprehensively realized.

[0075] therefore, Figure 1The frequency range of the terahertz wave generated by the pulse seed injection terahertz parameter source generation device can include 0.5Hz-13.6THz.

[0076] According to the terahertz parameter source generation device based on pulse seed injection provided by the embodiment of the present disclosure, the terahertz parameter generation technology based on stimulated electromagnetic coupler scattering effect, by adopting sub-nanosecond pulse laser pumping, nanosecond pulse laser seed injection, auxiliary bleaching laser synchronous control, and the combination of MgO:LiNbO3 and KTP two crystals, high-power, wide-tuning terahertz waves are realized. Compared with the terahertz parameter source using nanosecond pulse laser pumping, sub-nanosecond pulses have a significant inhibitory effect on the SBS effect. The pump laser is mainly used for the stimulated Raman scattering process, which is conducive to the improvement of the terahertz wave conversion efficiency. At the same time, sub-nanosecond pulses have high peak power, which is conducive to the forward progress of nonlinear optical processes. Compared with the terahertz parameter generation source using continuous laser seed injection, the nanosecond pulse seed has a higher peak power on the one hand, and it is easier to achieve coherent stimulated electromagnetic coupler scattering in a broadband range, thereby greatly improving the terahertz wave output power and expanding the terahertz tuning bandwidth. On the other hand, it is difficult for a continuous laser source to produce a seed laser with a continuously tunable wavelength of 532nm, while a nanosecond pulse laser source can be easily achieved through nonlinear optical frequency conversion technology. Compared with the terahertz parametric source using a single nonlinear optical crystal, the combination of MgO:LiNbO3 and KTP crystals can achieve an ultra-wideband tuning range covering the low and high frequency bands of terahertz, and has a wider application prospect. The terahertz source realized by this scheme has the advantages of ultra-wideband tuning, high average power, high peak power and good pulse sequence stability.

[0077] By adjusting the horizontal displacement and angle of the pump laser and the seed laser, the same-path output of terahertz waves at each frequency point can be achieved, which is convenient for the subsequent application of the terahertz source. In addition, the terahertz source can operate at room temperature and has good stability. The terahertz parameter source generation device based on pulse seed injection can be used in many other nonlinear optical crystals, such as KTA, RTP and other crystals. The transverse optical vibration mode of each crystal is different. The tuning characteristics of the terahertz waves generated by the device are different, which has a positive effect on expanding the terahertz tuning bandwidth and improving the terahertz output power. In addition, this method is also expected to be applied to systems such as terahertz imaging detection, up-conversion detection, and terahertz scattering characteristics measurement.

[0078] According to the embodiments of the present disclosure, the terahertz parameter generation technology based on the stimulated electromagnetic coupler scattering effect realizes high average power, high peak power and ultra-wideband tunable terahertz waves by adopting sub-nanosecond pulse laser pumping, nanosecond pulse laser seed injection, auxiliary bleaching laser synchronous control, and a combination of MgO:LiNbO3 and KTP crystals. The method is simple in principle, the generated terahertz pulse sequence is stable, can operate at room temperature, and can be applied to many other nonlinear optical crystals, and has important application value in terahertz imaging detection, up-conversion detection, and terahertz scattering characteristic measurement systems.

[0079] The embodiment of the present disclosure provides a method for generating a terahertz parameter source based on a pulse seed injection type terahertz parameter source generating device. The terahertz parameter source generating device based on the pulse seed injection type can be Figure 1 The terahertz parameter source generation device based on pulse seed injection is shown.

[0080] The terahertz parameter source generation method based on the pulse seed injection type terahertz parameter source generation device may include: using a laser synchronization unit to split the initial nanosecond pulse laser with a pulse width of the nanosecond order to obtain a reflected nanosecond pulse laser and a transmitted nanosecond pulse laser. Using a pump laser generation unit to generate a subnanosecond pulse pump laser with a pulse width of the subnanosecond order according to the reflected nanosecond pulse laser and the auxiliary drift effect. Using a seed laser source generation unit to adjust the wavelength of the transmitted nanosecond pulse laser to obtain a nanosecond pulse seed laser with a pulse width of the nanosecond order. Using the nonlinear optical crystal included in the terahertz parameter generation unit to generate terahertz waves under the joint irradiation of the subnanosecond pulse pump laser and the nanosecond pulse seed laser, thereby generating a terahertz parameter source.

[0081] It will be appreciated by those skilled in the art that the features described in the various embodiments of the present disclosure may be combined and / or combined in a variety of ways, even if such combinations or combinations are not explicitly described in the present disclosure. In particular, without departing from the spirit and teachings of the present disclosure, the features described in the various embodiments of the present disclosure may be combined and / or combined in a variety of ways. All of these combinations and / or combinations fall within the scope of the present disclosure.

[0082] The embodiments of the present disclosure are described above. However, these embodiments are only for illustrative purposes and are not intended to limit the scope of the present disclosure. Although the embodiments are described above, this does not mean that the measures in the various embodiments cannot be used in combination to advantage. The scope of the present disclosure is limited by the attached embodiments and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art may make a variety of substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. A terahertz parameter source generation device based on pulse seed injection, comprising: A laser synchronization unit (100) is used to split an initial nanosecond pulse laser with a pulse width in the nanosecond range to obtain a reflected nanosecond pulse laser and a transmitted nanosecond pulse laser; A pump laser generating unit (200) is used to generate a sub-nanosecond pulse pump laser with a pulse width of the sub-nanosecond order according to the reflected nanosecond pulse laser and the auxiliary drift effect; A seed laser source generating unit (300) is used to adjust the wavelength of the transmitted nanosecond pulse laser to obtain a nanosecond pulse seed laser with a pulse width of the nanosecond order; The terahertz parameter generation unit (400) comprises: The nonlinear optical crystal (401) is used to generate terahertz waves under the joint irradiation of the sub-nanosecond pulse pump laser and the nanosecond pulse seed laser, thereby generating a terahertz parameter source.

2. The device according to claim 1, wherein: The laser synchronization unit (100) comprises: A nanosecond pulse laser (101), used to generate the initial nanosecond pulse laser; The laser beam splitter (102) is used to split the initial nanosecond pulse laser to obtain the reflected nanosecond pulse laser and the transmitted nanosecond pulse laser.

3. The device according to claim 2, wherein: The pump laser generating unit (200) comprises: A sub-nanosecond pulse laser master oscillator (201), used for generating a first sub-nanosecond pulse laser with a pulse width of the sub-nanosecond order according to the reflected nanosecond pulse laser and the auxiliary drift effect; A sub-nanosecond pulse laser amplifier (202), used for amplifying the power of the first sub-nanosecond pulse laser to obtain a second sub-nanosecond pulse laser; A sub-nanosecond laser frequency doubler (203), used for adjusting the frequency of the second sub-nanosecond pulse laser to obtain a third sub-nanosecond pulse laser; The sub-nanosecond laser polarization controller (204) is used to modulate the polarization state of the third sub-nanosecond pulse laser to obtain a sub-nanosecond pulse pump laser whose polarization state is vertical polarization.

4. The device according to claim 3, wherein: The emission wavelengths of the laser crystals respectively included in the sub-nanosecond pulse laser master oscillator (201), the sub-nanosecond pulse laser amplifier (202) and the nanosecond pulse laser (101) are consistent; Synchronizing the pump timing of the pump sources corresponding to the sub-nanosecond pulse laser master oscillator (201), the sub-nanosecond pulse laser amplifier (202) and the nanosecond pulse laser (101); The sub-nanosecond pulse laser master oscillator (201) further comprises: a saturable absorber, which is used to receive the reflected nanosecond pulse laser and control the synchronization of the reflected nanosecond pulse laser and the first sub-nanosecond pulse laser based on the auxiliary drift effect.

5. The device according to claim 1, wherein: The terahertz parameter generation unit (400) further includes: A pump laser reflector (402) is used to reflect the sub-nanosecond pulse pump laser so as to reflect the sub-nanosecond pulse pump laser to a preset position of the nonlinear optical crystal (401); The seed laser reflecting mirror (403) is used to reflect the nanosecond pulse seed laser, so as to reflect the nanosecond pulse seed laser to the preset position of the nonlinear optical crystal (401).

6. The device according to claim 5, wherein: The pump laser reflector (402) and the seed laser reflector (403) are each mounted on a corresponding electrically controlled turntable, wherein the electrically controlled turntable is used to adjust the emission angles of the lasers reflected by the pump laser reflector (402) and the seed laser reflector (403); Two electrically controlled turntables corresponding to the pump laser reflector (402) and the seed laser reflector (403) are respectively mounted on corresponding electrically controlled displacement platforms, wherein the electrically controlled displacement platforms are used to translate the lasers reflected by the pump laser reflector (402) and the seed laser reflector (403) in a horizontal direction; The two laser beams reflected by the pump laser reflector (402) and the seed laser reflector (403) intersect around the preset position at a non-collinear angle of 0.5° to 7°.

7. The device according to any one of claims 1 to 6, wherein: The seed laser source generating unit (300) comprises: A nonlinear optical frequency converter (301) is used to adjust the wavelength of the transmitted nanosecond pulse laser to obtain a first nanosecond pulse seed laser with a wavelength within a preset wavelength range and a pulse width of the nanosecond order; A nanosecond laser frequency doubler (302), used for adjusting the frequency of the first nanosecond pulse seed laser to obtain a second nanosecond pulse seed laser; The nanosecond laser polarization controller (303) is used to modulate the polarization state of the second nanosecond pulse seed laser to obtain a nanosecond pulse seed laser whose polarization state is vertical polarization.

8. The device according to claim 7, wherein: The sub-nanosecond pulse laser master oscillator (201) comprises a microcavity structure with bonded crystal Nd:YAG+Cr:YAG as a laser crystal; The sub-nanosecond pulse laser amplifier (202) comprises a traveling wave amplification structure using bonded crystal YAG+Nd:YAG as a laser crystal; The sub-nanosecond laser frequency doubler (203) and the nanosecond laser frequency doubler (302) both comprise a half-wave plate of a first preset wavelength; The sub-nanosecond laser frequency doubler (203) adopts a constant temperature design, and the nanosecond laser frequency doubler (302) adopts a variable temperature design; The sub-nanosecond laser polarization controller (204) and the nanosecond laser polarization controller (303) both comprise a half-wave plate of a first preset wavelength and a second preset wavelength, wherein the half-wave plates of the first preset wavelength and the second preset wavelength are switched accordingly according to the wavelength of the laser light incident on the sub-nanosecond laser polarization controller (204) and the nanosecond laser polarization controller (303).

9. The device according to claim 7, wherein: The nonlinear optical crystal (401) comprises one of the following: magnesium oxide doped with lithium niobate and potassium titanyl phosphate; The nonlinear optical crystal (401) adopts an isosceles trapezoidal block design; The sub-nanosecond pulse pump laser and the nanosecond pulse seed laser are incident from one waist surface of the isosceles trapezoidal block, intersect at the bottom surface of the isosceles trapezoidal block, and are totally reflected by the bottom surface of the isosceles trapezoidal block before being emitted from another waist surface of the isosceles trapezoidal block; The nonlinear optical crystal (401) generates a terahertz wave perpendicular to the bottom surface of the isosceles trapezoidal block based on the joint irradiation of the sub-nanosecond pulse pump laser and the nanosecond pulse seed laser, and emits from the bottom surface of the isosceles trapezoidal block; The nonlinear optical crystal (401) is mounted on a height-adjustable lifting platform, wherein the lifting platform is used to adjust the nonlinear optical crystal (401) of a preset material to a corresponding preset height.

10. The device according to claim 1, wherein: The frequency range of the terahertz wave includes 0.5 Hz-13.6 THz.

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