CN118508219A - 900 Nm-band laser generation system and method based on potassium titanyl phosphate crystal - Google Patents

Abstract

The present invention proposes a 900nm band laser generation system and method based on potassium titanyl phosphate crystal, and the present invention relates to the field of laser technology. The system includes a 532nm laser, an optical parametric oscillator KTP OPO based on a type II phase-matched potassium titanyl phosphate crystal, and a lens group. The 532nm laser output by the 532nm laser pumps the KTP OPO to obtain a group of signal light and idler light that meet the type II phase matching condition, and then the signal light is transmitted through the tilted lens group, and the idler light and the 532nm pump light are reflected. The potassium titanyl phosphate crystal is rotated to achieve tuned output in the 898nm-911nm band. The output laser has the advantages of full solidification, miniaturization, wide tuning, high tuning resolution, high beam quality, etc., simplifies the structure of the multi-band laser, and provides a laser design scheme for realizing tuning within a wider range of the band, which is of great significance in improving the efficiency and accuracy of the laser.

Description

A 900nm band laser generation system and method based on potassium titanyl phosphate crystal

Technical Field

The invention belongs to the field of laser technology, and in particular relates to a 900nm band laser generation system and method based on potassium titanyl phosphate crystals.

Background Art

At present, 900nm band lasers have extensive and important applications in optoelectronic guidance, atmospheric detection, deep-sea communications and other fields. Compared with the 1064nm band, the 900nm band has a better spectral response rate on laser silicon detectors, and is located at the transition absorption line of atoms and ions, and can be used to double the frequency to produce blue lasers, which has important applications in related fields. Therefore, we urgently need a 900nm band laser output solution with high conversion efficiency, wide tuning range and high tuning resolution.

At present, the main solid-state lasers in the 900nm band are titanium sapphire lasers and Nd3+-doped solid-state lasers. Titanium sapphire lasers can achieve tunable output. In 2017, Zhang Lianping et al. [1] used a 532nm laser to pump titanium sapphire crystals to achieve tunable laser output in the 852-934nm band. Nd3+-doped solid-state lasers can also output lasers in the 900nm band. In 2020, Yan Renpeng et al. used laser diodes to pump Nd:GdTaO ₄ to achieve transitions from ⁴ F _3/2 to ⁴ I _9/2 and ⁴ F _3/2 to ⁴ I _13/2 , thereby successfully outputting 928nm lasers.

In the 900nm band, the more commonly used commercial lasers are semiconductor lasers, which can achieve advantages such as high conversion efficiency, low cost, and miniaturization. However, compared with solid-state lasers, their tuning range is small, the beam quality is not high, and it is difficult to output high-energy pulsed lasers. Option 1 The titanium sapphire laser has a wide tuning range and a large output energy (average output power of more than 2W), but its optical system is relatively complex, making it difficult to achieve miniaturization and lightweight, and the tuning speed is slow and maintenance is complex. Option 2 Neodymium ion transitions have competition problems between three-level transitions (900nm) and four-level transitions (1060nm), and the output efficiency of 1.06μm lasers is higher. And the wavelength cannot achieve tuned output.

Summary of the invention

In order to solve the above technical problems, the present invention proposes a 900nm band laser generation system and method based on potassium titanyl phosphate crystals.

The first aspect of the present invention discloses a 900nm band laser generation system based on potassium titanyl phosphate crystal, the system comprising: a 532nm laser, an optical parametric oscillator KTP OPO based on type II phase-matched potassium titanyl phosphate crystal, and a lens group;

The 532nm laser output by the 532nm laser pumps the KTP OPO to obtain a set of signal light and idler light that meet the type II phase matching condition. Then, the tilted lens group is used to transmit the signal light and reflect the idler light and 532nm pump light.

The output is tuned within the 898nm-911nm band by rotating the potassium titanyl phosphate crystal.

Optionally, the KTP OPO is composed of a cavity mirror M1, a cavity mirror M2, a potassium titanyl phosphate crystal, and a crystal adjustment frame;

The cavity mirror M1 and cavity mirror M2 transmit 532nm pump light and signal light, and reflect idler light. The potassium titanyl phosphate crystal is placed in the center of the two cavity mirrors and transmits 532nm pump light, signal light and idler light.

Optionally, the type II phase matching cutting angle of the potassium titanyl phosphate crystal is (67° to 68.5°, 0°).

Optionally, the lens group includes a first lens and a second lens;

The first lens reflects 532nm pump light and transmits signal light, and the second lens reflects idler light and transmits signal light.

Optionally, the system further comprises a beam adjustment component, located between the 532 nm laser and the KTP OPO, for compressing the radius of the 532 nm laser beam.

Optionally, the 532nm laser includes a YAG laser, a frequency doubling crystal and a beam splitter;

The YAG laser outputs 1.06μm pulse laser, which generates 532nm laser after passing through the frequency doubling crystal. After the 1.06μm pulse laser and 532nm laser are split by a beam splitter, the 532nm laser beam is used to pump the KTP OPO.

Optionally, the frequency doubling crystal is one of an LBO crystal, a KTP crystal or a BBO crystal.

The second aspect of the present invention discloses a 900nm band laser generation method based on potassium titanyl phosphate crystals, the method is implemented by a 900nm band laser generation system based on potassium titanyl phosphate crystals as described in any one of the above embodiments, the method comprising:

The 532nm laser output from the 532nm laser pumps the KTP OPO to obtain a set of signal light and idler light that meet the type II phase matching condition;

The signal light is transmitted through the tilted lens group, and the idler light and 532nm pump light are reflected;

The output is tuned within the 898nm-911nm band by rotating the potassium titanyl phosphate crystal.

Optionally, the KTP OPO is composed of a cavity mirror M1, a cavity mirror M2, a potassium titanyl phosphate crystal, and a crystal adjustment frame;

The cavity mirror M1 and cavity mirror M2 transmit 532nm pump light and signal light, and reflect idler light. The potassium titanyl phosphate crystal is placed in the center of the two cavity mirrors and transmits 532nm pump light, signal light and idler light.

Optionally, the type II phase matching cutting angle of the potassium titanyl phosphate crystal is (67° to 68.5°, 0°).

In summary, the scheme proposed in the present invention has the following technical effects: Optical Parametric Oscillator (OPO) can convert mature 1064nm laser into ultraviolet, visible light, near infrared, mid-infrared and far infrared band lasers, and has the advantages of all-solid-state design, miniaturization, high efficiency, high beam quality, and wide tunable output wavelength. Optical parametric oscillator technology converts the pump light down in frequency to obtain a group of signal light and idler light with different frequencies. Through the study of optical parametric oscillator technology, it is found that the technology requires the pump wavelength to be smaller than the signal light and the idler light. Therefore, in order to obtain a laser in the 900nm band, this application considers using 532nm as the pump light. KTiOPO4 (KTP for short) crystal is a nonlinear frequency doubling crystal material with excellent comprehensive performance, with a large light transmission band (0.35-3.5μm), a high laser damage threshold (500MW/cm2) and a large nonlinear optical coefficient (d _eff =7.34pm/V). The present application proposes to use a 532nm laser to pump a KTP crystal to generate a 900nm band laser, and the tuning resolution thereof is better than 1nm.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

FIG1 is a schematic diagram of a 900 nm laser generating system based on potassium titanyl phosphate crystal according to an embodiment of the present invention;

FIG2 is a phase matching curve of KTP OPO under 532 nm pumping according to an embodiment of the present invention;

FIG3 is a structural diagram of a 900 nm band laser generating system based on potassium titanyl phosphate crystal according to an embodiment of the present invention.

DETAILED DESCRIPTION

In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

It is understood that the terms "first", "second", etc. used in this application may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish a first element from another element. For example, a first image may be referred to as a second image, and similarly, a second image may be referred to as a first image without departing from the scope of this application. Both the first image and the second image are images, but they are not the same image.

According to an embodiment of the present invention, a first aspect of the present invention discloses a 900nm band laser generation system based on potassium titanyl phosphate crystal, please refer to Figure 1, the system includes: a 532nm laser, an optical parametric oscillator KTP OPO based on type II phase-matched potassium titanyl phosphate crystal, and a lens group.

The 532nm laser output from the 532nm laser pumps the KTP OPO to obtain a set of signal light and idler light that meet the type II phase matching condition. Then, the signal light is transmitted through the tilted lens group, and the idler light and 532nm pump light are reflected. The output is tuned in the 898nm-911nm band by rotating the potassium titanyl phosphate crystal.

Optionally, the KTP OPO is composed of a cavity mirror M1, a cavity mirror M2, a potassium titanyl phosphate crystal, and a crystal adjustment mirror frame. The cavity mirror M1 and cavity mirror M2 are coated with a 1.28μm-1.30μm high-reflection film and a 532nm and 898nm-911nm anti-reflection film. The cavity mirror M1 and cavity mirror M2 transmit 532nm pump light and signal light (898nm-911nm), and reflect idler light (1.28μm-1.30μm). The potassium titanyl phosphate crystal is placed in the center of the two cavity mirrors and transmits 532nm pump light, signal light, and idler light.

Optionally, the type II phase matching cutting angle of potassium titanyl phosphate crystal is (67° to 68.5°, 0°). Optionally, by pumping a KTP crystal with a cutting angle of (67.8°, 0°) with a 532nm laser, a 911nm laser output can be obtained under normal incidence conditions, and its tuning accuracy can reach 0.4074nm. It can also output a laser in the 900nm band and achieve continuous tuning of the wavelength. When a 532nm laser is used to pump KTP crystals at other angles, such as KTP (68°, 0°), KTP (67°, 0°), etc., a 900nm band laser can also be generated.

Optionally, the lens group includes a first lens and a second lens; the first lens is coated with a 532nm high reflection film and an 898nm-911nm anti-reflection film. The second lens is coated with a 1.28μm-1.30μm high reflection film and an 898nm-911nm anti-reflection film. The first lens reflects 532nm pump light and transmits signal light, and the second lens reflects idler light and transmits signal light.

Optionally, the system further comprises a beam adjustment component, located between the 532nm laser and the KTP OPO, for compressing the radius of the 532nm laser beam. Optionally, the beam adjustment component is a telescope system.

Optionally, the 532nm laser includes a YAG laser, a frequency doubling crystal, and a beam splitter. The YAG laser outputs a 1.06μm pulse laser, which generates a 532nm laser after passing through the frequency doubling crystal, and then the 1.06μm pulse laser and the 532nm laser are split by the beam splitter, and the 532nm laser beam is split to pump the KTP OPO.

Optionally, the frequency doubling crystal is one of an LBO crystal, a KTP crystal or a BBO crystal. Optionally, as shown in FIG1 , the frequency doubling crystal is an LBO crystal, and the Nd:YAG (YAG (yttrium aluminum garnet) laser) outputs a 1.06 μm pulse laser with a pulse width of several nanoseconds to tens of nanoseconds, and the LBO crystal is highly transparent to the pump light (1.06 μm) and the frequency doubling light (532 nm). D1 and D2 are small apertures, and the E mirror is used as a beam splitter, which is highly reflective to the pump light (1.06 μm) and highly transparent to the frequency doubling light (532 nm). T is a telescope system that can compress the spot radius to make the energy of the pump light more concentrated. KTP OPO is composed of M1, M2 mirrors and a KTP crystal. M1 and M2 mirrors are highly transparent to pump light (532nm), highly reflective to signal light (898-911nm), and highly transparent to idler light (1.28-1.30μm). KTP crystal is placed in the center of two cavity mirrors and highly transparent in three bands: pump light (532nm), signal light (898-911nm), and idler light (1.28-1.30μm). F1 and F2 mirrors are placed at a small angle. F1 is highly reflective to pump light (532nm) and highly transparent to signal light (898-911nm). F2 is highly reflective to idler light (1.28-1.30μm) and highly transparent to signal light (898-911nm).

Figure 2 shows the phase matching curve of the idler light output by the KTP OPO pumped by a 532nm laser when the KTP crystal has a φ = 0° condition. It can be seen that the output wavelength of the KTP OPO changes with the rotation angle of the crystal, and finally achieves tuning in the 898-911nm band.

The invention provides a method for generating a wide-tuned 900nm band near-infrared laser based on potassium titanyl phosphate crystals and lithium triborate crystals. The device can be used to obtain tunable laser output in the 900nm band, and the output laser has the advantages of full solidification, miniaturization, wide tuning, high tuning resolution, high beam quality, etc., simplifies the structure of a multi-band laser, provides a laser design scheme for achieving tuning within a wider range of the band, and is of great significance in improving the efficiency and accuracy of the laser.

As shown in FIG3 , a KTP OPO with a cutting angle of (67.8°, 0°) is pumped by a 532 nm laser and can output a 911 nm laser under normal incidence.

The KTP OPO can be angle tuned by using the adjustment mirror frame above the crystal. For a Class II matched KTP (67.8°, 0°) crystal, the adjustment mirror frame rotates one circle, and the internal tilt angle of the crystal changes by Δθ = 0.136°. When the θ angle is tuned and the tuning range is 67°-68.5°, the output wavelength can be continuously tuned between 898-911nm (Class II).

Table 1 Angle tuning data

The “-” represents left rotation, and the “+” represents right rotation.

It can be seen that when the angles are 68.48°, 68.34°, 68.21°, 68.07°, 67.94°, 67.8°, 67.66°, 67.53°, 67.39°, 67.26°, and 67.12°, the measured peak wavelengths are 911nm, 910nm, 908nm, 907nm, 906nm, 904nm, 903nm, 902nm, 901nm, 899nm, and 898nm, respectively, and Δλ _i /Δθ=9.56nm/°.

The second aspect of the present invention discloses a 900nm band laser generation method based on potassium titanyl phosphate crystals, the method is implemented by a 900nm band laser generation system based on potassium titanyl phosphate crystals as described in any one of the above embodiments, the method comprising:

The 532nm laser output from the 532nm laser pumps the KTP OPO to obtain a set of signal light and idler light that meet the type II phase matching condition;

The signal light is transmitted through the tilted lens group, and the idler light and 532nm pump light are reflected;

The output is tuned within the 898nm-911nm band by rotating the potassium titanyl phosphate crystal.

Optionally, the KTP OPO is composed of a cavity mirror M1, a cavity mirror M2, a potassium titanyl phosphate crystal, and a crystal adjustment frame;

The cavity mirror M1 and cavity mirror M2 transmit 532nm pump light and signal light, and reflect idler light. The potassium titanyl phosphate crystal is placed in the center of the two cavity mirrors and transmits 532nm pump light, signal light and idler light.

Optionally, the type II phase matching cutting angle of the potassium titanyl phosphate crystal is (67° to 68.5°, 0°).

In summary, the scheme proposed in the present invention has the following technical effects: Optical Parametric Oscillator (OPO) can convert mature 1064nm laser into ultraviolet, visible light, near infrared, mid- and far infrared band lasers, and has the advantages of all-solid-state design, miniaturization, high efficiency, high beam quality, and wide tunable output wavelength. Optical parametric oscillator technology converts the pump light down in frequency to obtain a group of signal light and idler light with different frequencies. Through the study of optical parametric oscillator technology, it is found that the technology requires the pump wavelength to be smaller than the signal light and the idler light. Therefore, in order to obtain a laser in the 900nm band, this application considers using 532nm as the pump light. KTiOPO4 (KTP for short) crystal is a nonlinear frequency doubling crystal material with excellent comprehensive performance, with a large light transmission band (0.35-3.5μm), a high laser damage threshold (500MW/cm2) and a large nonlinear optical coefficient (d _eff =7.34pm/V). The present application proposes to use a 532nm laser to pump a KTP crystal to generate a 900nm band laser, and the tuning resolution thereof is better than 1nm.

The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that the technical solutions described in the above embodiments can still be modified, or some or all of the technical features therein can be replaced by equivalents, and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims (10)

1. A 900nm band laser generation system based on potassium titanyl phosphate crystal, characterized in that the system comprises: a 532nm laser, an optical parametric oscillator KTP OPO based on type II phase-matched potassium titanyl phosphate crystal, and a lens group; The 532nm laser outputted by the 532nm laser pumps the KTP OPO to obtain a set of signal light and idler light that meet the type II phase matching condition. Then, the tilted lens group is used to transmit the signal light and reflect the idler light and 532nm pump light. The output is tuned within the 898nm-911nm band by rotating the potassium titanyl phosphate crystal. 2. The system according to claim 1, characterized in that the KTP OPO is composed of a cavity mirror M1, a cavity mirror M2, a potassium titanyl phosphate crystal and a crystal adjustment frame; The cavity mirror M1 and cavity mirror M2 transmit 532nm pump light and signal light, and reflect idler light. The potassium titanyl phosphate crystal is placed in the center of the two cavity mirrors and transmits 532nm pump light, signal light and idler light. 3. The system according to claim 2, characterized in that the type II phase matching cutting angle of the potassium titanyl phosphate crystal is (67° to 68.5°, 0°). 4. The system according to claim 1, wherein the lens group comprises a first lens and a second lens; The first lens reflects 532nm pump light and transmits signal light, and the second lens reflects idler light and transmits signal light. 5. The system according to claim 1, characterized in that the system also includes a beam adjustment component located between the 532nm laser and the KTP OPO, for compressing the radius of the 532nm laser beam. 6. The system according to claim 1, characterized in that the 532nm laser comprises a YAG laser, a frequency doubling crystal and a beam splitter; The YAG laser outputs 1.06μm pulse laser, which generates 532nm laser after passing through the frequency doubling crystal. After the 1.06μm pulse laser and 532nm laser are split by a beam splitter, the 532nm laser beam is used to pump the KTP OPO. 7. The system according to claim 6, characterized in that the frequency doubling crystal is one of an LBO crystal, a KTP crystal or a BBO crystal. 8. A method for generating a 900 nm laser based on a potassium titanyl phosphate crystal, characterized in that the method is implemented by using a 900 nm laser generating system based on a potassium titanyl phosphate crystal according to any one of claims 1 to 7, and the method comprises: The 532nm laser output from the 532nm laser pumps the KTP OPO to obtain a set of signal light and idler light that meet the type II phase matching condition; The signal light is transmitted through the tilted lens group, and the idler light and 532nm pump light are reflected; The output is tuned within the 898nm-911nm band by rotating the potassium titanyl phosphate crystal. 9. The method according to claim 8, characterized in that the KTP OPO is composed of a cavity mirror M1, a cavity mirror M2, a potassium titanyl phosphate crystal and a crystal adjustment frame; The cavity mirror M1 and cavity mirror M2 transmit 532nm pump light and signal light, and reflect idler light. The potassium titanyl phosphate crystal is placed in the center of the two cavity mirrors and transmits 532nm pump light, signal light and idler light. 10 . The method according to claim 9 , wherein the type II phase matching cutting angle of the potassium titanyl phosphate crystal is (67° to 68.5°, 0°).