TW200420931A - Single-fanout cascaded grating quasi-phase-matched nonlinear optical crystal and wavelength conversion and tunable laser system using the same - Google Patents

Abstract

A single-fanout cascaded grating quasi-phase-matched nonlinear optical monolithic crystal and wavelength conversion and tunable laser system using the same are disclosed. The monolithic crystal includes a quasi-phase-matched single period grating having a first grating period along a first direction; and a quasi-phase-matched fanout grating having a second grating period along the first direction, wherein the second grating period is tunable along a second direction, the level of the second grating period continuously varies depending on the displacement of the crystal along the second direction, and the first direction is perpendicular to the first direction. By cascading the single period grating with the fanout grating, the wavelength conversion of the laser can be performed at a constant temperature or within a specific temperature range. When a laser system employs such monolithic crystal, although the single-fanout cascaded grating quasi-phase-matched nonlinear optical monolithic crystal is kept at a constant temperature, the most appropriate grating period can be selected continuously by moving the position of the crystal transversely (I.e. along the second direction). Whereby, the quasi-phase-matched conditions of two gratings are reached so as to achieve the purpose of converting the wavelength continuously. In addition, the wavelength of the laser can be converted in wider wavelength range by changing the temperature of the crystal and matching the single period grating with the grating period of the fanout grating.

Description

200420931, ^ * V. Description of the invention (l) The technical field to which the invention belongs This invention relates to the design of gratings for single crystals of nonlinear optics, especially for quasi-phase matching (Q uasi — P hase-M atching; QP Μ) nonlinear optics Design of linear and fan-shaped series grating of monolithic crystal and laser generating device using the crystal as a frequency converter. Previous technologies With the rapid evolution of laser technology, various lasers have been widely used in different fields. Traditionally, most laser light emits a fixed wavelength or frequency by using the transition of electrons or carriers between different energy levels. • Coherent electromagnetic radiation. Taking solid-state lasers as an example, solid-state lasers have become the mainstream of all types of lasers due to the simple and lightweight system and the booming development of optoelectronic materials science in recent years. Semiconductor lasers are the most typical example. Semiconductor lasers are popular because of their small size, low power consumption for operation, easy mass production, and low cost. However, due to the limitation of the energy level of the semiconductor material, it can only produce some specific wavelength output, and the output power is low, which cannot meet many applications that require high-power coherent light sources. These characteristics limit the application of semiconductor lasers. However, many applications require laser sources with adjustable wavelengths. For example, in the detection of environmental trace gases, because different gases have different absorption wavelengths, lasers with adjustable wavelengths combined with a spectral detection system can be applied to the detection and analysis of multiple trace gases. Another example, in full-color lasers

Page 10 200420931 V. Description of the invention (2) In the flat display, each image point (piXe1) is generated by selective focusing of a laser light source that emits three wavelengths of red, green and blue. Although some laser light sources, such as dye lasers, free-electron lasers, and some nonlinear crystal lasers, can all adjust the wavelength of their laser emission to a certain extent, but their The wavelength tunable range is still not large enough, and it is expensive, has low energy conversion efficiency, and is inconvenient to operate. In recent years, with the rapid development of nonlinear optics, tunable-wavelength lasers have also made great progress. The more commonly used second-order polarized nonlinear optical effects are caused by one or two incident laser sources (in some cases, such as frequency doubling, the two incident sources can be obtained from the same laser source) following the same path Ground passes through a non-linear optical crystal to produce a mixing effect, thereby emitting 'an expected special wavelength laser. The second-order nonlinear optical effect includes second-order harmonic generation (SHG), difference frequency generation (DFG), and sum frequency generation (SFG), and Optical parameter generation, optical parameter amplification, and optical parameter oscillation

Generation, Amplification, Oscillation; OPG, OPA 0 P 0) and so on. In the process of second-order nonlinear conversion, if the emitted laser signal and the other two laser light signals reach phase-matching in the crystal, the intensity of the emitted laser will pass through the crystal

The cumulative increase in length. If the two channels X and X do not match the phase of the laser light, the intensity of the emitted laser will be strengthened in accordance with the law. In a non-linear optical crystal, the desired laser emission can be achieved. ^ Π & ^ ^^

200420931 V. Description of the invention (3) A coherence length. Therefore, in the case of phase mismatch, the intensity of the emitted laser can only be accumulated at most through a single coherence length, and usually the homology length is only a few micrometers (m m) in this case. Therefore, in order to achieve the phase matching of the three signals, it is necessary to design the nonlinear optical characteristics of the crystal cleverly so that the laser intensity to be generated continuously increases in the nonlinear crystal. Since the temperature can also change the refractive index of the crystal, thereby changing the conditions of phase matching, changing the nonlinear crystal temperature is one of the methods to adjust the laser wavelength. Quasi-phase-matched nonlinear lasers have recently been developed to improve the efficiency of tunable wavelength lasers. See n Quasi-Phase-Matched Second Harmonic Generation: Tuning W and Tolerances, f, IEEE Journal of Quantum by Fejer at el.

Electronics, vol. 28, 1992 pp. 2631-2654, and U.S. Patent Nos. 5,036,220, 5,800,767, 5,714,198, and 5,838,702. Quasi-phase matching (QPM) technology is mainly used to make periodic lattice polarization inversion on non-linear optical crystals to compensate for the phase velocity of light waves that interact with frequency conversion in the crystal due to dispersion effects. The difference is, in this way, any wavelength interaction and conversion can be achieved on such crystals in a non-critical phase-matching (n 0 ncr 丨 t 丨 ca 1 phase-matching) manner within its light-transparent wavelength range. With this quasi-phase matching compensation method, the interacting light waves can use the largest 0 element in the nonlinear coefficient tensor of the crystal to achieve a higher nonlinear conversion efficiency. In the framework of the aforementioned technology, the second-order nonlinear optical coefficient of the crystal

200420931 V. Description of the invention (4) Periodically change the number with each homology length as a unit to achieve the purpose of phase matching (this is called quasi-phase matching) and effectively generate laser light at another frequency. Therefore, we can use the quasi-phase matching technology to select the largest nonlinear optical coefficient in the nonlinear crystal to achieve the maximum laser energy conversion efficiency. Periodically changing the number is usually accomplished by periodically changing the direction of the spontaneous polarization of the ferroelectric material. In addition to the wavelength and operating temperature of the pump laser, the interval period of the alternately polarized region determines the wavelength of the emitted laser. When the pump laser wavelength and the grating period of the ferroelectric material are fixed, the wavelength of the laser can be adjusted slightly by changing the temperature. Many ferroelectric materials can form fairly good quasi-phase · position-matching nonlinear optical crystals, such as lithium niobate (Li Nb03), lithium tantalate (LiTa03), potassium niobate (KNb03), potassium titanyl phosphate (KTi0P04; KTP), titanyl arsenate (1? 1) 1 [丨 (^ 3〇4; 1 ^ eight), titanyl osmium phosphate (1 ^ 1 ^ 0? 04), and so on. The first figure (A) shows a conventional quasi-phase-matching nonlinear optical crystal 1 0 1, which has only a single grating period, so there is only one kind of nonlinear optical effect in the crystal to achieve phase matching. For example, published by Myers et al. 'Quasi-phase-matching 1.064 / m-pumped optical parametric oscillator in bulk periodically poled LiNb03, MOPTICS LETTERS ¥ 〇1.2〇 ^ 〇.1, with 11.1995, 0? .52-54 . The first figure (8) shows 〇 Another conventional quasi-phase-matching nonlinear optical crystal 1 02, which is composed of two part single crystals with different grating periods.

Page 13 200420931 V. Description of the invention (5) The ability to achieve phase matching with 5 kinds of nonlinear optical effects. For example, Rosenberg published 2.5-W continuous-wave, 629-nm solid-state laser source ", Optics Letters, Vo 1. 23 No. 1, February 1, 1998, pp. 207-209, and US Patent No. 5,768,302. number. In this type of Quasi-Phase-Matching (QPM) nonlinear optical crystal, the nonlinear optical parameters of the crystal will be changed periodically in the direction of laser travel. For example, the quasi-phase matching (Q u a s i-P h a s e-M a t c h i n g; Q P M) technology enables the second-order nonlinear conversion process to meet the following quasi-phase matching conditions:

η3 (Τ) / λ3-η2 (Τ) / λ2-ni (T) / = 1 / Eight simultaneously meet the energy conservation conditions in quantum optics 1 / λ3 _ 1 / λ2 ~ 1 / λ X = 0 (2) where , Λ is the period of the lattice inversion grating of the quasi-phase-matched nonlinear optical crystal, and I, 2, 3 are the vacuum wavelengths of the three mixed waves, and n !, 2 JT) are the three waves with the wavelength u and 3, respectively Refractive index within the crystal. Since the value of the refractive index depends on the substance and the temperature, the crystal temperature T will determine the value of the refractive index in the formula (1). For a known grating period and any mixing wavelength, 'two simultaneous equations (1, 2) can solve the skin length of two other unknown mixed waves. However, the two gratings composed of a single crystal are at the same temperature when performing non-linear optical response / response. When the crystal temperature is adjusted, it is difficult to meet the wavelengths generated by the quasi-phase matching grating region at the same temperature. The second quasi-phase bit matches the quasi-phase matching condition of the grating region. At this moment, when the temperature changes slightly, it ’s possible that the phase of one of the gratings is not matched.

200420931 V. Description of Invention (6) Matching. This difficulty not only causes the actual laser output results to be inconsistent with the design, but also results in a limited adjustable laser wavelength, and cannot provide a laser that can continuously adjust the wavelength at a fixed crystal temperature or within a temperature range. nessecery. Therefore, in view of the lack of known technology, the present invention has been carefully tested and researched, and has persevered in the spirit, and finally created the "single-period and fan-shaped grating series quasi-phase matching nonlinear optical single crystal in this case." And using the crystal's wavelength-tunable laser generation device ", a practical, novel and progressive laser generation architecture is disclosed, which allows continuous nonlinear frequency conversion and large-scale wavelength adjustment at a fixed temperature or a temperature range of the crystal. 4 Summary of the Invention The main purpose of this case is to disclose a quasi-phase-matching nonlinear optical single crystal with a single period and a fan-shaped grating series, which can perform laser frequency conversion. A secondary object of the present case is to provide a nonlinear optical crystal which can perform laser frequency conversion at a fixed temperature or a temperature range. To achieve the above object, the present invention provides a quasi-phase-matched nonlinear optical single crystal, which at least includes: a quasi-phase-matched single-period grating region having a first grating period in a first direction; and a quasi-phase-matched sector grating The region has a second grating period that is adjustable along a second direction and a first grating period in the first direction, and the period size of the second grating period is continuously changed as the displacement in the second direction changes. its

Page 15 200420931 5. In the description of the invention (7), the second direction is perpendicular to the first direction. Another object of the present invention is to provide a wavelength-tunable laser generating device using the above-mentioned quasi-phase matching single crystal. The laser generating device can use the crystal to continuously select a second grating period of the quasi-phase matching sector grating region at a fixed temperature or a temperature range to perform laser frequency conversion to provide a laser whose wavelength is continuously adjustable. To achieve the above object, the present invention provides a wavelength-tunable laser generating device, which at least includes: a quasi-phase-matching nonlinear optical single crystal, which has a quasi-phase-matching single grating region and a quasi-phase-matching fan-shaped grating region, wherein The quasi-phase matching single grating region has a first grating period in a first direction, and the quasi-phase matching sector grating region has a second grating that is tunable along the first direction along a second surface ^ direction. Period, and the period size of the second grating period is continuously changed as the displacement of the second direction changes, wherein the second direction is perpendicular to the first direction; and at least one laser input light source is used to provide A first laser signal of at least one wavelength enters the quasi-phase-matching nonlinear optical single crystal along the first direction. Therefore, after the first laser signal is incident into the quasi-phase-matching nonlinear optical single crystal, at least two non-linear optical frequency or wavelength conversion effects are generated in the crystal according to the characteristics of each grating, so that the emission has at least one difference from The second laser signal at the input wavelength. According to the idea of this case, the arrangement order of the single-period optical thumb region and the fan-shaped grating region in the crystal of this case is not fixed. The pump laser light source can first enter the single-period grating region and then into the fan-shaped grating region, or it can also enter the fan-shaped grating first. The area is shot into the single-cycle grating area. When the pump laser light source enters the first grating region

Page 16 200420931 V. Description of the invention (8), the frequency of the pump laser will be converted for the first time, and after the second grating area is continued, the frequency of the pump laser will be converted for the second time. According to the idea of the present case, the wavelength-tunable laser generating device further includes a temperature-controlling oven to change the quasi-phase characteristics of the crystal to increase the wavelength modulation range. According to the concept of the present case, the wavelength-tunable laser generating device may further include a resonant cavity, which may be two reflecting mirrors disposed on both sides of the non-linear optical crystal, or may be directly plated on both end surfaces of the non-linear optical crystal. Two reflective films. According to the idea of the present case, the laser generating device may further include a ring-shaped resonant cavity structure including at least two reflectors, φ are located on both sides of the nonlinear optical crystal along the first direction, And at least two mirrors, which are located outside the non-linear optical crystal. According to the concept of the present case, the laser generating device further includes a focusing lens or an optical lens system, which is used to focus the first laser signal and guide it to the non-linear optical crystal. This case can be explained in detail by the following diagrams, so as to make a deeper understanding: The diagrams are briefly explained. The first diagram (A): is a single-cycle quasi-phase-matched nonlinear optical crystal of conventional technology. Μ The first picture (B): It is a longitudinally connected double-period quasi-phase-matching nonlinear optical crystal of another conventional technique.

Page 17 200420931 V. Description of the invention (9) The second figure: a schematic diagram of the first preferred embodiment of the quasi-phase-matched nonlinear optical single crystal of this case. The third figure is a schematic diagram of another preferred embodiment of the quasi-phase-matched nonlinear optical single crystal of the present invention. Fig. 4 is a schematic view of the first preferred embodiment of the laser generating device of the present invention, wherein the laser generating device does not use a resonance mirror group. The fifth figure is the schematic diagram of the second preferred embodiment of the laser generating device of the present invention, wherein two sides of the crystal are provided with two resonance mirrors. Fig. 6 is a schematic view of a third preferred embodiment of the laser generating device of the present invention, in which two optical films are plated on both ends of the crystal. The seventh figure: the fourth preferred embodiment of the laser generating device of this case. Explanation of symbols 1 〇1: Single-period quasi-phase-matching nonlinear optical crystal 1 02: Vertically cascaded bi-period-linear nonlinear optical crystal 2 0 1: Series-connected early-period and fan-shaped quasi-phase-matching nonlinear optical single crystal 2 0 1 1: Early light area 2 0 1 2: Sector grating area 3 0 1: Pump laser light source 3 0 2: Focusing lens or optical lens system 303, 304, 305, 306: Single cycle in series And sector grating quasi-phase matching nonlinear optical single crystal

Page 18 200420931 V. Description of the invention 3031,3041,3051,3061: Single-cycle grating area 3 0 3 2, 3 0 4 2, 3 0 5 2, 3 0 6 2: Fan-shaped grating area 401, 403, 405, 407: Temperature-controlled furnaces 501, 502: Resonant cavity mirrors 503, 504: Optical films 505, 506: Resonant cavity mirror implementation method I. Quasi-phase matching nonlinear optical single crystal The second picture shows the quasi-phase matching nonlinear optical single in this case Crystal. The cascaded single-circle and sector-shaped grating quasi-phase-matched nonlinear optical single crystal 2 0 1 is preferably a ferroelectric with single-crystal lattice inversion, such as lithium niobate (LiNb03), lithium tantalate (LiTa03), Potassium niobate (KNb03), potassium titanyl phosphate (KTi0P04; KTP), titanyl arsenate (RbTiOAs04; RTA), titanyl osmium phosphate (RbTiOP04), or the like. In this embodiment, the grating design of the single-period and fan-shaped quasi-phase matching optical single crystal 201 connected in series includes two parts-a single-period grating 2011 and a fan-out grating. 2012. The single-circle grating region 2011 has a non-linear optical characteristic along a first direction, and the first direction is a grating periodic direction and a laser traveling direction. The fan-shaped grating region 2 0 1 2 has a non-linear optical characteristic that is modulated along the first direction, wherein the second direction is perpendicular to the first direction. When the above-mentioned non-linear optical single crystal 201 is used, the fan can be selected by the position of the paleoperipheral crystal 201 in the lateral direction (that is, the second or y direction).

Page 19 200420931 V. Description of the invention The optimum grating period of the (11) shaped grating region 2 0 1 2 is to optimize the nonlinear frequency conversion of the crystal 2 0 1. In addition, the single-cycle grating region 2 0 1 1 and the fan-shaped grating region 2 0 1 in the single-cycle and sector-shaped grating quasi-phase matching optical single crystal 2 01 are not connected in a fixed order. 〇1 1 is arranged before the fan grating area 2 0 1 2 (relative to the pump laser source), and the fan grating area 2 0 1 2 can also be arranged before the single-circle grating area 2 0 1 1 (as shown in the third figure). Show). With the above-mentioned crystal grating structure, when the laser emitted by the pump laser light source (not shown) enters the first grating region (such as the single-circle grating region of the second figure 2 0 1 1 or the fan shape of the third figure) After the grating area 2 0 1 2), the frequency of the pump laser will be converted for the first time. When it continues to enter the second grating area (such as the fan-shaped grating area 2012 of the second picture or the single-circle grating area of the third picture) After 2011), the frequency of the pumped laser was converted a second time, so the quasi-phase-matched laser frequency conversion can be achieved by this crystal. However, it must be noted that the grating design in the crystal of the present case may have other modifications and changes, and is not limited to the preferred embodiments disclosed above.贰. A wavelength-tunable laser generating device using a quasi-phase matching optical single crystal connected in series with a single period grating and a sector grating and the embodiment A · wavelength-tunable second-order secondary resonance (SHG) plus light parameter generation (〇PG) thunder ≪ 1 The fourth figure shows the first preferred embodiment of the laser generating device of the present invention. The laser generating device mainly includes a group of laser light sources 301, a focusing lens or optical lens system 302, and a series of single-circle and fan-shaped grating standards.

Page 20 200420931 V. Description of the invention (12) Phase matching optical single crystal 3 03. The pump laser light source 301 is used to emit an input laser signal having a first wavelength to enter a tandem single-cycle and fan-shaped grating quasi-phase-matched nonlinear optical single crystal 303. The focusing lens or optical lens system 3 2 is used to focus the input laser signal and guide it to the correct position. After the laser signal generated by the pump laser light source 3 〇1 is injected into the cascaded single-circle and sector-shaped grating quasi-phase matching optical single crystal 3 〇3, the crystal 303 will perform the aforementioned laser frequency conversion, and A laser beam of a predetermined wavelength will be emitted. In this embodiment, the series-connected single-circle and fan-shaped quasi-phase matching optical single crystal 3 03 can be set in a temperature-controlled furnace 4 01 to change and control the temperature of the crystal 3 03. The temperature control furnace 4 01 is used to change the quasi-phase characteristics of the crystal 3 03 so as to use the temperature change to output a laser beam of a specific range of 1 wave length. In the above embodiment, it is preferable to connect a single-cycle and sector-shaped grating quasi-phase-matched optically non-linear single crystal 303 with periodically poled lithium nibobate (PPLN) after periodic lattice polarization inversion. Among them, the length of a single grating region 3031 may be about 1-3 cm, and its grating period (Λ) is 6.67 mm, and the pump light source 301 may be driven by a second-order SHG at 100 ° C. The 1064-nm pump laser frequency multiplied is converted into a 5 3 2 nm laser and output to the sector grating region 3032. In addition, the length of the fan-shaped grating region 3032 may be about 4 cm, and the width of the grating period (Λ) of 5 mm in the lateral direction (that is, the second or y direction) may be continuously adjusted between 11 mm and 12 mm. At 100t: When the 532nm laser is incident into the fan M-shaped grating region 3 0 3 2, the fan-shaped grating region 3 0 3 2 will output a wavelength range from 618nm to 590nm with a tunable optical parameter generation process (0PG). Laser. In other words

Page 21 200420931 V. Description of the invention (13), the 5 3 2 nm laser generated by phase matching of 3 0 3 1 at 100 ° C in a single-cycle grating region is used. When the 5 3 2 nm laser is in a sector shape When the grating region 3030 scans a grating period of 1 1-12 mm laterally (that is, along the second or y direction), the sector grating region 3 0 3 2 can be the same through the optical parameter generation (0PG) process. A laser beam with a wavelength in the range of 618nm to 590nm and a continuously adjustable wavelength is produced at a temperature. In this way, the laser generating device can generate a continuously adjustable wavelength laser at a single fixed temperature I of the crystal. & In addition, the pump laser light source 301 is preferably a Q-switched laser (Nd3 + Q-sw itched laser), whose emission wavelength is 10.64 nm. Since the highest peak power of pump lasers can exceed tens of kilowatts (ki lowatt), pump lasers pass through a single-cycle grating region of 3031 φ and can convert the laser energy through a simple resonance nonlinear conversion mechanism Almost all are converted into lasers with a wavelength of 5 3 2nm. This 5 3 2 ηη laser will continue to pass through the fan-shaped grating region 3 0 3 2 ′ and generate laser light in the fan-shaped grating region 30 2 2 through an optical parameter process. B. Wavelength-tunable optical parameter oscillation (0 P 0) plus second-order second-resonance (s HG) laser during the non-linear laser wavelength conversion process, which is used to resonate one or more laser signals to reduce the pump threshold ( Pumping thresh (ld) and enhancing the overall laser conversion efficiency can be achieved by adding a resonant cavity as shown in the fifth to seventh embodiments. The fifth drawing shows a second preferred embodiment of the laser generating device of the present invention. In this embodiment, the 'laser · radiation generating device mainly includes a group of lasers.

Page 22 200420931 V. Description of the invention (14) Light source 301, a focusing lens or optical lens system 302, a series of single-circle and sector grating quasi-phase matching optical single crystal 304, and a resonant cavity ( Consists of mirrors 50 1 and 50 2). The laser generating device can generate a laser beam with a wavelength ranging between 775 nm and 800 nm and a continuously adjustable wavelength when the temperature of the crystal 300 is adjusted between 30 and 500. In the above embodiment, the 'pump laser light source 3 0 1 is used to emit an input laser signal having a first wavelength to enter the crystal 3 0 4. The focusing lens or optical lens system 3 2 is used to focus the input laser signal and guide it to the correct position. After the laser signal generated by the pump laser light source 3 0 1 is injected into the quasi-phase matching optical single crystal 3 0 4, the crystal 3 0 4 will perform the aforementioned laser frequency conversion and emit a preset wavelength range. Laser. Crystal 4 has a resonant cavity composed of two mirrors 501 and 50 2 on both sides of body 3 0 4 to circulate one or more laser signals to reduce the pumping threshold and enhance the overall laser. Conversion efficiency. In addition, the tandem single-circle and sector-shaped grating quasi-phase matching optical single crystal 304 can be set in a temperature-controlled furnace 403 to change and control the temperature of the crystal 304. The temperature control furnace 403 is used to change the quasi-phase characteristics of the crystal 304 so as to adjust the output laser wavelength by using the temperature change. In the above embodiment, the pump laser light source 3 0 1 is preferably a titanium-doped Q-switched laser (Nd3 + Q-switched laser) with an emission wavelength of 10 6 4 n m. In addition, cascaded single-period and sector-shaped grating quasi-phase-matched nonlinear optical single crystal 3 0 4 is preferably periodically poled lithium nibobate (PPLN) which undergoes periodic lattice polarization inversion, and the crystal 3 The 0 4 series consists of two parts of the grating area. The two parts of light

Page 23 200420931 V. Description of the invention (15) The grating area is a single-circle grating area 3041 with a grating period of 30mm, and the grating period can be changed in width of 5mm in the lateral direction (that is, the second or y direction) to 19 Fan-shaped grating area 3 mm in one mm. The single-cycle grating region 3 0 4 1 is used as a gain medium for the optical parameter oscillation (0P0) process in this embodiment, and the fan-shaped grating region 3 0 4 2 is used as a third-order quasi-phase matching second harmonic generator (third — Order QPM SHG) ° 'When the temperature of the crystal 304 is 30 ° C, the resonant cavity of the single-circle grating region 3041 (the periodic lattice polarization inversion sharp acid chain with a grating period of 30 mm) will be 1 The optical wave oscillation of 55 Onm wavelength is called optical parameter oscillation. Similarly, when the temperature of the crystal f is 30 ° C, the crystal 3 0 4 can be modulated laterally (that is, along the second or y direction) so that a light wave with a wavelength of 1550 nm is scanned into the sector grating region 3 〇 2 2 19mm grating period. A fan-shaped grating region 3 042 with a grating period of 19 mm will cause a light wave with a wavelength of 15 5 Onm to generate its frequency-doubling light wave at 30 ° C to generate a laser with a wavelength of 775 nm. In order to generate more wavelength range and continuously adjustable laser ', the temperature can be adjusted to 150. (: In this case, the quasi-phase matching condition in the single-circle grating region 3 40 1 will cause the optical parameter oscillation (oop) process to vibrate with light waves with a wavelength of 16 0 nm. That is, along the second or y direction), the series-connected single-circle and sector-shaped grating quasi-phase-matched nonlinear optical single crystal 3 0 4 ′ can scan a light wave with a wavelength of 1 6 00 n in to the sector-shaped grating region 3 0 4 2 of the 19.8mm grating period. A fan-shaped grating region 3042 with a grating period of 19 8mm will cause a light wave with a wavelength of 1600nm to generate its frequency-doubling light wave at 150 ° C to generate a laser with a wavelength of 800nm. With this laser generating device When the temperature of the crystal 3 0 4 is adjusted between 30 ° C and 150 ° C, a laser with a continuously adjustable wavelength ranging from 775nm to 800ηπΓ can be generated.

Page 24 200420931 V. Description of the Invention (16) The second picture is not the second preferred embodiment of the laser generation system in this case. In order to reduce the size of the laser generating device, the mirrors 501, 502 in the fifth figure can be plated on two optical films 503 on both ends of a single-period and fan-shaped grating quasi-phase-matching nonlinear optical single crystal 305 in series. , 504 replaced. Of course, the spectral reflectance and radius of curvature of the optical films 503, 504 can be changed according to the system requirements. In addition, in this embodiment, the components of the laser generating device, such as a pump laser light source 3 01, a focusing lens or an optical lens system 3 02, a series of single-circle and sector-shaped grating quasi-phase matching optical single crystal The design, principle, and application of 305 (with single-circle grating region 3051 and fan-shaped grating region 3052) and temperature-controlled furnace 405 are similar to the components shown in the fifth figure, so they are not described again. However, it should be noted that if the curvature radius of the optical film 503, 504 is infinite, and two plane mirrors are formed, this embodiment is generally more suitable for a pulsed pump source. The seventh figure shows a fourth preferred embodiment of the laser generating device of the present invention. In this embodiment, in order to increase the advantage of the laser generating device operating at a single frequency, the mirrors 5 0 1, 5 0 2 in the fifth figure may be tilted by a specific angle, and two resonant cavity mirrors 505, 506 may be added. This is achieved by forming a Bow-Tie ring resonator structure. In this embodiment, two mirrors 501, 502 are located on both sides of the tandem and sector grating quasi-phase matching optical single crystal 3 0 6 along the first direction, and two other cavity mirrors 5 0 5 and 5 0 6 are located outside the crystal 3 0 6. Of course, in this embodiment, the components of the laser generating device, such as pump laser light source 301, a focusing lens ❶ or an optical lens system 302, a series of single-cycle and sector-shaped grating quasi-phase matching optical single Crystal 3 0 6 (with single grating region 3 0 6 1 and sector grating region 3 062)

Page 25 200420931 V. Description of the invention (17) The design, principle and application of the temperature control furnace 407 are similar to the components shown in the fifth figure, so they will not be described again. As mentioned above, the grating design of the quasi-phase-matching nonlinear optical monolithic crystal in this case includes a single-period grating region and a sector grating region, where the sector grating region is in the lateral direction (that is, along the second or y direction). With adjustable grating period. Thus, when the crystal is applied to a laser generation system, although the entire quasi-phase-matching nonlinear optical single crystal is maintained at a fixed temperature, the crystal can be moved by moving the crystal laterally (that is, in the second or X direction). A most suitable grating period is selected so that the quasi-phase matching conditions of the two grating regions can be satisfied at the same time, and the purpose of continuously adjusting the wavelength can be achieved. In addition, you can adjust the crystal temperature to achieve a wider range of wavelength tunable lasers. This case may be modified by anyone who is familiar with the technology, but none of them can be protected as attached to the scope of patent application.

Page 26 200420931 Brief description of the diagram The first diagram (A): is a single-cycle quasi-phase-matching nonlinear optical crystal of conventional technology. The first figure (B) is a longitudinally-connected double-period quasi-phase-matched nonlinear optical crystal of another conventional technique. The second figure is a schematic diagram of the first preferred embodiment of the quasi-phase-matching nonlinear optical single crystal of this case. The third figure is a schematic diagram of another preferred embodiment of the quasi-phase-matching nonlinear optical single crystal of this case. The fourth figure is a schematic diagram of the first preferred embodiment of the laser generating device in this case, wherein the laser generating device does not use a resonance mirror group. Fig. 5 is a schematic diagram of a second preferred embodiment of the laser generating device of the present invention, in which two sides of the crystal have two resonance mirrors. Fig. 6 is a schematic diagram of the third preferred embodiment of the laser generating device of the present invention, in which two ends of the crystal are plated with two optical films. Fig. 7 is a schematic diagram of a fourth preferred embodiment of the laser generating device of the present invention.

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Claims (1)

200420931 VI. Scope of patent application 1 · A quasi-phase-matching nonlinear optical single crystal at least includes: a quasi-phase-matching single-period grating region having a first grating period along a first direction; and a quasi-phase-matching sector The grating region has a second grating period tunable along a first direction along a second direction, and the period size of the second grating period is continuously changed as the displacement of the second direction changes. The second direction is perpendicular to the first direction. 2. The crystal according to item 1 of the scope of patent application, wherein the quasi-phase-matching nonlinear optical single crystal system is an electrically polarizable crystal. 3. The crystal according to item 2 of the scope of patent application, wherein the electrically polarizable Φ crystal is a ferroelectric material. 4. The crystal according to item 3 of the scope of the patent application, wherein the ferroelectric substance is selected from the group consisting of lithium sharp acid (LiNb03), group acid bell (LiTa03), sharp acid discharge (KNb03), potassium titanyl phosphate (KTi0P04; KTP), RtTi0As04 (RTA), RtTi0P04 or other similar. 5 · The crystal according to item 1 of the scope of patent application, wherein the quasi-phase matching single-period grating region can be arranged before or after the quasi-phase matching sector grating region. 6. A laser generating device, including at least: U a quasi-phase-matching nonlinear optical single crystal having a stomach-quasi-phase-matching single-period grating region and a quasi-phase-matching fan-shaped grating region, wherein the quasi-phase matching A single grating region has a first along a first direction Page 28 200420931 VI. Patent application scope grating period, the quasi-phase matching sector grating region has a second grating period that is tunable along the first direction along a second direction, and the second grating period has its period The magnitude is continuously changed as the displacement of the second direction changes, wherein the second direction is perpendicular to the first direction; and at least one laser input light source is used to provide a first laser signal edge having at least one wavelength. The first direction is incident on the quasi-phase-matching nonlinear optical single crystal; thereby, after the first laser signal is incident on the quasi-phase-matching nonlinear optical single crystal, at least two are generated inside the crystal according to the characteristics of each grating. A non-linear optical frequency or wavelength conversion effect to emit a second laser signal having at least one different wavelength from the input wavelength. 7. The laser generating device according to item 6 of the patent application scope, wherein the laser generating device further comprises a temperature-controlled furnace for controlling the temperature of the quasi-phase-matching nonlinear optical single crystal and modulating the gratings The phase matching characteristics can be used to modulate the output laser wavelength and enhance the output power. 8. The laser generating device according to item 6 of the patent application scope, wherein the laser generating device further comprises a resonant cavity for increasing the intensity of at least the second laser signal. 9. The laser generating device according to item 8 of the scope of the patent application, wherein the resonance cavity is composed of a first mirror and a second mirror located on both sides of the crystal. 10. The laser generating device according to item 8 of the scope of the patent application, wherein the resonant cavity is composed of two optically reflective films plated on both end surfaces of the crystal. 1 I The laser generating device according to item 6 of the scope of patent application, wherein the Page 29 200420931 VI. Patent application scope Non-linear optical frequency or wavelength conversion effects include Second Harmonic Generation (SHG and THG), Difference Frequency Generation (DFG), and Sum Frequency Generation; SFG), optical parameter generation, optical parameter amplification, and optical parameter oscillation (0 ptica 1 Parametric Generati ο η, Amplification, Oscillation; 0PG, OPA, 0P0) 〇1 2 · Thunder as described in item 6 of the scope of patent application The radiation generating device, wherein the quasi-phase-matching nonlinear optical single crystal system is an electrically polarizable crystal. 1 3 · The laser generating device according to item 12 of the patent application scope, wherein the electrically polarizable crystal is a ferroelectric material ° 14 · The laser according to item 13 of the patent application scope A generating device, wherein the ferroelectric substance is selected from the group consisting of lithium niobate (LiNb03), lithium tantalate (LiTa03), potassium niobate (KNb03), potassium titanyl phosphate (KTi0P04; KTP), and titanyl arsenate (RbTi0As04; RTA), RtTiOPOJ, or the like. 1 5 · The laser generation device described in item 6 of the patent application scope, wherein the quasi-phase matching single-period grating region can be arranged in the quasi-phase matching sector grating Before or after the zone. 16. The laser generating device according to item 6 of the patent application scope, wherein the laser generating device further comprises a ring-shaped resonant cavity structure for increasing the intensity of at least the second laser signal. 17. The laser generating device according to item 16 in the scope of the patent application, wherein the ring-shaped resonant cavity structure includes at least two mirrors, which are located in the crystal / Page 30 200420931 Page 31