Solid blue laser with continuously tunable wavelength

Abstract

The invention provides a solid blue laser with continuously tunable wavelength, and belongs to the technical field of lasers. The laser comprises a laser emitting device, an optical parametric oscillator OPO, a first plane mirror F1, a second plane mirror F2, an LBO crystal, a third plane mirror F3 and a spectrograph which are sequentially arranged along a light transmission axis. The optical parametric oscillator OPO sequentially comprises a first cavity mirror M1, a KTP crystal and a second cavity mirror M2; and the optical transmission axis is positioned in the center of each component. The laser provided by the invention is used for generating blue laser of which the wavelength can be continuously tuned.

Description

Technical Field

[0001] This invention belongs to the field of laser technology, and particularly relates to a solid-state blue laser with continuously tunable wavelength. Background Technology

[0002] Currently, blue lasers (440nm-490nm) have a wide range of important applications in underwater communication, ocean exploration and other fields. Compared with ordinary blue lasers, wavelength-tunable high peak power solid-state blue lasers have more spectral information and can be used as underwater lidar light sources, showing broad application prospects.

[0003] Compared to red and green lasers, the generation of blue lasers is more complex. Generally, Nd: 3+ The 946 nm or 1319 nm laser, after frequency second or third harmonic, produces 473 nm and 440 nm blue light. However, due to Nd... 3+ The commonly used output wavelength is 1064 nm. Outputting 946 nm or 1319 nm requires mode selection, and the output 473 nm and 440 nm blue laser wavelengths cannot be tuned, resulting in a single detection mode.

[0004] Currently, solid-state lasers in the blue light band are mainly generated by second or third harmonics. For example, Scheme 1: using a 946 nm Nd:YAG laser to pump a LiIO3 crystal to generate a 473 nm laser; or Scheme 2: using a 1319 nm Nd:YAG laser to pump an LBO crystal to generate a 440 nm laser.

[0005] For Scheme 1: Based on the characteristics of the 946 nm laser transition, a preliminary intracavity frequency doubling experiment was conducted. Using a LiIO3 crystal, the experiment produced 100 pW of 473 nm blue light. (For example...) Figure 1 As shown, a 946nm laser is generated using a laser diode array pumping system, and this laser is then used to generate 473nm blue light through intracavity frequency doubling. The pumping system includes two GaAlAs laser diode arrays, a polarization beam splitter (PBS), a 1mm long Nd:YAG crystal, a planar input mirror, and an output mirror with a radius of 5cm. This scheme, by inserting a LiIO3 crystal into the Nd:YAG crystal, can generate 473nm blue laser light.

[0006] For Scheme 2: Utilizing a 1.3μm laser generated by a side-pumped Nd:YAG laser, high-power blue light output with a wavelength of 440nm and an average power of 4.3W was achieved by third-harmonic generation of the intracavity frequency. For example... Figure 2As shown, a 1.3 μm laser is generated using an all-solid-state Nd:YAG laser system, and 440 nm blue light is obtained by frequency conversion of this laser through an LBO crystal. The laser system includes two identical side-pumped Nd:YAG laser modules, a folded three-mirror resonator, an acousto-optic modulator (AO-Q switch), a Brewster plate, and two LBO crystals (one for second harmonic generation and one for third harmonic generation).

[0007] However, the blue laser output wavelength of Scheme 1 is not tunable, and 946 nm is not the optimal emission peak for Nd3+ ions, resulting in limited output energy. The blue laser output wavelength of Scheme 2 is also not tunable, and 1319 nm is not the optimal emission peak for Nd3+ ions, leading to limited output energy. Compared to second harmonics, third harmonics have lower conversion efficiency. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention proposes a solid-state blue laser with continuously tunable wavelength. In the proposed solution, a 532nm laser is used to pump a KTP crystal to generate a 900nm wavelength laser (center wavelength 900nm, tuning range 890-910 nm). Then, an LBO crystal is used to frequency double this laser to a 450nm wavelength (center wavelength 450nm, tuning range 445-455 nm), achieving a wavelength tuning range of approximately 10 nm.

[0009] The laser proposed in this invention is used to generate blue laser light with continuously tunable wavelength. The laser includes: a laser emitting device, an optical parametric oscillator (OPO), a first plane mirror F1, a second plane mirror F2, an LBO crystal, a third plane mirror F3, and a spectrometer, arranged sequentially along the optical transmission axis; the OPO sequentially includes: a first cavity mirror M1, a KTP crystal, and a second cavity mirror M2; the optical transmission axis is located at the center of each of the above components; wherein: When the laser is in operation, a 532nm laser is emitted by the laser emitting device to pump the optical parametric oscillator (OPO) to obtain a set of signal light and idler light that meet the II-B phase matching conditions. Tunable output in the 890-910nm band is achieved by rotating the KTP crystal; specifically, this includes: pumping the KTP crystal with a 532nm laser at a cutting angle of θ=67.3° and φ=0° to obtain a 900nm laser under normal incidence conditions; and then tuning the angle of the KTP crystal. A 900 nm laser is frequency doubled to 450 nm using an LBO crystal with a cutting angle of θ=90° and φ=22.9°. The frequency doubling efficiency of the LBO crystal has an allowable linewidth, and the laser at 900 nm generates frequency-doubled light, thereby obtaining a blue laser with a wavelength that can be continuously tuned in the range of 445-455 nm. θ represents the angle between the cutting direction and the Z-axis in the three-dimensional coordinate system, φ represents the angle between the projection of the cutting direction onto the XOY plane and the XOZ plane in the three-dimensional coordinate system, and O is the origin of the three-dimensional coordinate system.

[0010] According to the laser proposed in this invention, the tuning of the KTP crystal angle specifically includes: outputting 890 nm laser when θ = 66.3°; and outputting 910 nm laser when θ = 68.3°.

[0011] According to the laser proposed in this invention, the optical parametric oscillator (OPO) comprises a first cavity mirror M1, a KTP crystal, and a second cavity mirror M2; wherein: M1 and M2 have high transmittance for 532nm laser light, high transmittance for 890-910nm signal light, and high reflectivity for 1.28-1.33μm idler light. The KTP crystal, placed between M1 and M2, exhibits high transmittance in 532nm laser light, 890-910nm signal light, and 1.28-1.33μm idler light.

[0012] According to the laser proposed in this invention, for the first plane mirror F1 and the second plane mirror F2: Both F1 and F2 have tilt angles; F1 exhibits high reflectivity to 532nm laser light and high transmittance to signal light in the 890-910nm range; F2 exhibits high reflectivity for idler light in the 1.28-1.33μm range and high transmittance for signal light in the 890-910 nm range.

[0013] According to the laser proposed in this invention, the LBO crystal has high transmittance for signal light of 890-910 nm and high transmittance for frequency-doubled light of 445-455 nm.

[0014] According to the laser proposed in this invention, the third plane mirror F3 has high reflectivity for signal light of 890-910 nm and high transmittance for frequency-doubled light of 445-455 nm.

[0015] According to the laser proposed in this invention, a spectrometer measures the output light.

[0016] According to the laser proposed in this invention, when the cutting angle φ=0° of the KTP crystal, the phase matching curve of the output idler light of the 532nm laser pump optical parametric oscillator OPO is such that the output wavelength of the optical parametric oscillator OPO changes with the rotation angle of the KTP crystal, thereby achieving tuning in the 890-910nm band.

[0017] According to the laser proposed in this invention, when the LBO crystal is pumped by a 900nm wavelength laser, it outputs a 450nm frequency-doubled light phase-matching curve, which doubles the frequency of the tuned pump light to 445-455 nm, thereby achieving tunable blue light output in this wavelength band.

[0018] In summary, in the proposed solution of this invention, when a 532nm laser is used to pump a KTP OPO, a tunable laser in the 900 nm band can be obtained by utilizing the type II-B phase matching of the KTP crystal. Then, this laser in the 900 nm band is passed through an LBO crystal to obtain a tunable laser in the 450 nm band (tuning range 445-455 nm). Compared with other solid-state lasers, it has the advantages of wide tuning range and high peak power. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the principle of Scheme 1 in the prior art; Figure 2 This is a schematic diagram of the principle of Scheme 2 in the prior art; Figure 3 This is a schematic diagram of a laser configuration according to an embodiment of the present invention; Figure 4 The phase matching curve of the optical parametric oscillator (OPO) under 532nm pump according to an embodiment of the present invention; Figure 5 This is the frequency doubling phase matching curve of an LBO crystal under 900nm pump according to an embodiment of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Definitions of abbreviations and key terms: KTP: KTiOPO4, potassium titanium phosphate, is a nonlinear crystal.

[0023] LBO: LiB3O5, lithium triborate, a frequency doubling crystal.

[0024] OPO: Optical Parametric Oscillator, which consists of a nonlinear crystal and an optical resonant cavity, can achieve continuous tuning of the output wavelength over a wide range.

[0025] SHG: Second Harmonic Generation, also known as frequency multiplication, is a process in which two photons of the same frequency interact to produce a new photon with twice the frequency and half the wavelength of the original photon in a nonlinear material.

[0026] This invention proposes a solid-state blue laser with continuously tunable wavelength. The laser is used to generate blue laser light with continuously tunable wavelength. Figure 3 As shown, the laser includes: a laser emitting device, an optical parametric oscillator (OPO), a first plane mirror F1, a second plane mirror F2, an LBO crystal, a third plane mirror F3, and a spectrometer arranged sequentially along the optical transmission axis; the optical parametric oscillator (OPO) includes: a first cavity mirror M1, a KTP crystal, and a second cavity mirror M2; the optical transmission axis is located at the center of each of the above components.

[0027] This invention, based on practical needs and applications, utilizes a 532nm laser to pump a KTP OPO to obtain a set of signal and idler beams that meet the Class II-B phase matching conditions. By rotating the KTP, modulated output can be achieved in the 890-910nm wavelength range. Using a KTP crystal pumped with a 532nm laser at a cutting angle (θ=67.3°, φ=0°), 900nm laser light can be obtained under normal incidence conditions. By tuning the angle of the KTP crystal, 890nm laser light is output when θ=66.3°, and 910nm laser light is output when θ=68.3°.

[0028] Then, using an LBO crystal with a cutting angle of (θ=90°, φ=22.9°), the 900 nm laser is frequency doubled to 450 nm. Since the frequency doubling efficiency of the LBO crystal has a certain allowable linewidth, the laser near 900 nm will also produce frequency doubled light, so a tunable blue laser of 445-455 nm can be obtained.

[0029] The KTP OPO consists of mirrors M1 and M2 and a KTP crystal. Mirrors M1 and M2 are highly transparent to pump light (532nm), highly transparent to signal light (890-910 nm), and highly reflective to idler light (1.28-1.33μm). The KTP crystal is placed in the center of the two cavity mirrors and is highly transparent in the three wavelength bands of pump light (532nm), signal light (890-910 nm), and idler light (1.28-1.33μm).

[0030] Mirrors F1 and F2 are tilted at a small angle. Mirror F1 is highly reflective of pump light (532nm) and highly transmittant of signal light (890-910nm). Mirror F2 is highly reflective of idler light (1.28-1.33μm) and highly transmittant of signal light (890-910nm).

[0031] LBO crystals have high transmittance for signal light (890-910 nm) and high transmittance for frequency-doubled signal light (445-455 nm).

[0032] F3 exhibits high reflectivity for signal light (890-910 nm) and high transmittance for the frequency-doubled version of the signal light (445-455 nm). The output light is measured using a spectrometer.

[0033] like Figure 4 The figure shows the phase-matching curve of the idler light output by a 532nm laser-pumped KTP OPO when the KTP crystal has a rotation angle of φ=0°. It can be seen that the output wavelength of the KTP OPO changes with the rotation angle of the crystal, achieving tuning in the 890-910nm band.

[0034] like Figure 5 As shown, the phase-matching curve of the LBO crystal outputting 450nm frequency-doubled light when pumped by a 900nm laser is illustrated. The tuned pump light can be frequency-doubled to 445-455 nm, ultimately achieving high-power tunable blue light output in this wavelength range.

[0035] First embodiment: Using a 532nm laser to pump a KTP OPO with a cut angle of (θ=67.3°, φ=0°), a 900nm laser can be output under normal incidence. Then, using an LBO crystal with a cut angle of (θ=90°, φ=22.9°), the 904nm laser is converted to 450nm.

[0036] Among them, mirrors M1 and M2 have high transmittance for pump light (532nm), high transmittance for signal light (890-910 nm), and high reflectance for idler light (1.28-1.33μm). The KTP crystal placed in the center of the two cavity mirrors has high transmittance in three wavelength bands: pump light (532nm), signal light (890-910nm), and idler light (1.28-1.33μm).

[0037] Mirrors F1 and F2 are tilted at a small angle. Mirror F1 is highly reflective of pump light (532nm) and highly transparent of signal light (890-910nm). Mirror F2 is highly reflective of idler light (1.28-1.33μm) and highly transparent of signal light (890-910nm).

[0038] LBO crystals have high transmittance for signal light (890-910 nm) and high transmittance for frequency-doubled signal light (445-455 nm).

[0039] F3 exhibits high reflectivity for signal light (890-910 nm) and high transmittance for the frequency-doubled version of the signal light (445-455 nm). The output light is measured using a spectrometer.

[0040] By using an angle-adjusting lens frame to tune the KTP crystal, for a Class II matched KTP crystal (θ=67.3°, φ=0°), when the θ angle of the KTP crystal is tuned within a range of 66.3°-68.3°, the output wavelength can be continuously tuned between 890-910nm (Class II-B).

[0041] Table 1: Relationship between output wavelength and angle

[0042] As shown in Table 1, for the KTP crystal, under normal incidence, the angle θ of the KTP crystal is 67.3°. At this time, the output wavelength of KTPOPO is 900nm, and the output wavelength of LBO SHG is half of that, 450nm.

[0043] When the angle adjustment frame begins to rotate, the angle θ of the KTP crystal changes between 66.3° and 68.3°, and the peak wavelength of KTP OPO changes from 890nm to 910nm.

[0044] For LBO SHG, the conversion efficiency is the highest under normal incidence, after which the conversion efficiency begins to decrease, and the output wavelength is 445-455 nm.

[0045] Second embodiment: Using a 532nm laser to pump a KTP OPO with a cut angle of (θ=69.3°, φ=0°), a 920nm laser can be output under normal incidence. Then, using an LBO crystal with a cut angle of (θ=90°, φ=21.3°), the 920nm laser is converted to 460nm.

[0046] Among them, mirrors M1 and M2 have high transmittance for pump light (532nm), high transmittance for signal light (910-930 nm), and high reflectance for idler light (1.24-1.28μm). The KTP crystal placed in the center of the two cavity mirrors has high transmittance in three wavelength bands: pump light (532nm), signal light (910-930nm), and idler light (1.24-1.28μm).

[0047] Mirrors F1 and F2 are tilted at a small angle. Mirror F1 is highly reflective of pump light (532nm) and highly transparent of signal light (910-930nm). Mirror F2 is highly reflective of idler light (1.24-1.28μm) and highly transparent of signal light (910-930nm).

[0048] LBO crystals have high transmittance for signal light (910-930 nm) and high transmittance for frequency-doubled signal light (455-465 nm).

[0049] F3 exhibits high reflectivity for signal light (910-930 nm) and high transmittance for the frequency-doubled version of the signal light (455-465 nm). The output light is measured using a spectrometer.

[0050] By using an angle-adjusting lens frame to tune the KTP crystal, for a Class II matched KTP crystal (θ=69.3°, φ=0°), when the θ angle of the KTP crystal is tuned within a range of 68.3°-70.3°, the output wavelength can be continuously tuned between 910-930nm (Class II-B).

[0051] As shown in Table 2, for KTP crystal, under normal incidence, the angle θ of KTP crystal is 69.3°. At this time, the output wavelength of KTP OPO is 920 nm, and the output wavelength of LBO SHG is half of that, 460 nm.

[0052] Table 2: Relationship between output wavelength and angle

[0053] When the angle adjustment frame begins to rotate, the angle θ of the KTP crystal changes between 68.3° and 70.3°, and the peak wavelength of KTP OPO changes from 910 nm to 930 nm.

[0054] For LBO SHG, the conversion efficiency is the highest under normal incidence, after which the conversion efficiency begins to decrease, and the output wavelength is 455-465 nm.

[0055] In summary, the laser provided by this invention generates blue laser light based on KTP and LBO crystals. It can be used to obtain tunable laser output in the 450 nm band, and the output laser has advantages such as high peak power, all-solid-state, and miniaturization. It provides a high-performance blue laser source for realizing multispectral lidar detection in this band, and provides important support for improving underwater laser communication and precision marine detection.

[0056] Furthermore, when using a 532nm laser to pump KTP crystals at other angles, such as KTP (71.3°, 0°), tunable lasers in other wavelength bands, such as the 940 nm band, can also be generated. Then, frequency doubling to the 470 nm band yields tunable blue laser light in that band.

[0057] Please note that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A solid-state blue laser with continuously tunable wavelength, characterized in that: The laser is used to generate blue laser light with continuously tunable wavelength; the laser includes: a laser emitting device, an optical parametric oscillator (OPO), a first plane mirror F1, a second plane mirror F2, an LBO crystal, a third plane mirror F3, and a spectrometer arranged sequentially along the optical transmission axis; the optical parametric oscillator (OPO) contains, in sequence: a first cavity mirror M1, a KTP crystal, and a second cavity mirror M2; the optical transmission axis is located at the center of each of the above components; wherein: When the laser is in operation, a 532nm laser is emitted by the laser emitting device to pump the optical parametric oscillator (OPO) to obtain a set of signal light and idler light that meet the II-B phase matching conditions. Tunable output in the 890-910nm band is achieved by rotating the KTP crystal; specifically, this includes: pumping the KTP crystal with a 532nm laser at a cutting angle of θ=67.3° and φ=0° to obtain a 900nm laser under normal incidence conditions; and then tuning the angle of the KTP crystal. A 900 nm laser is frequency doubled to 450 nm using an LBO crystal with a cutting angle of θ=90° and φ=22.9°. The frequency doubling efficiency of the LBO crystal has an allowable linewidth, and the laser at 900 nm generates frequency-doubled light, thereby obtaining a blue laser with a wavelength that can be continuously tuned in the range of 445-455 nm. θ represents the angle between the cutting direction and the Z-axis in the three-dimensional coordinate system, φ represents the angle between the projection of the cutting direction onto the XOY plane and the XOZ plane in the three-dimensional coordinate system, and O is the origin of the three-dimensional coordinate system.

2. A wavelength-tunable solid-state blue laser according to claim 1, characterized in that, The specific tuning of the KTP crystal angle includes: outputting 890 nm laser when θ=66.3°; and outputting 910 nm laser when θ=68.3°.

3. A wavelength-tunable solid-state blue laser according to claim 2, characterized in that, The optical parametric oscillator (OPO) comprises a first cavity mirror M1, a KTP crystal, and a second cavity mirror M2; wherein: M1 and M2 have high transmittance for 532nm laser light, high transmittance for 890-910nm signal light, and high reflectivity for 1.28-1.33μm idler light. The KTP crystal, placed between M1 and M2, exhibits high transmittance in 532nm laser light, 890-910nm signal light, and 1.28-1.33μm idler light.

4. A wavelength-tunable solid-state blue laser according to claim 3, characterized in that, For the first plane mirror F1 and the second plane mirror F2: Both F1 and F2 have tilt angles; F1 exhibits high reflectivity to 532nm laser light and high transmittance to signal light in the 890-910nm range; F2 exhibits high reflectivity for idler light in the 1.28-1.33μm range and high transmittance for signal light in the 890-910 nm range.

5. A wavelength-tunable solid-state blue laser according to claim 4, characterized in that, LBO crystals have high transmittance for signal light in the 890-910 nm range and high transmittance for frequency-doubled light in the 445-455 nm range.

6. A wavelength-tunable solid-state blue laser according to claim 5, characterized in that, The third plane mirror F3 is highly reflective of signal light in the 890-910 nm range and highly transparent of frequency-doubled light in the 445-455 nm range.

7. A wavelength-tunable solid-state blue laser according to claim 6, characterized in that, The spectrometer measures the output light.

8. A wavelength-tunable solid-state blue laser according to claim 7, characterized in that, When the cutting angle φ=0° of the KTP crystal, the phase matching curve of the output idler light of the 532nm laser-pumped optical parametric oscillator (OPO) is shown. The output wavelength of the OPO changes with the rotation angle of the KTP crystal, thereby achieving tuning in the 890-910nm band.

9. A wavelength-tunable solid-state blue laser according to claim 8, characterized in that, When the LBO crystal is pumped by a 900nm laser, the phase matching curve of the output frequency-doubled light at 450nm is obtained. The frequency of the tuned pump light is doubled to 445-455nm, thus achieving tunable blue light output in this band.

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