A device for improving OPA energy conversion efficiency

Abstract

The present invention discloses an OPA energy conversion efficiency improvement device, which includes two nonlinear optical OPA crystals and a 1 / 2 wave plate, wherein the 1 / 2 wave plate is placed between the nonlinear optical OPA crystal 1 and the nonlinear optical OPA crystal 2, and is placed perpendicular to the laser propagation direction, and the distance between the 1 / 2 wave plate and the front and rear nonlinear optical OPA crystals 1 and the nonlinear optical OPA crystal 2 is equal. The present invention avoids the signal light energy loss caused by the reverse frequency sum process, and greatly improves the amplification efficiency of the OPA device.

Description

Technical Field

[0001] The invention relates to an experimental device capable of improving the energy conversion efficiency of an optical parametric amplifier (OPA), and belongs to the field of optoelectronic technology. Background Art

[0002] The earliest research on optical parametric oscillators (OPOs) and amplifiers (OPAs) can be traced back to the 1960s. In 1962, Kingston, Kroll and others proposed the concept of optical parametric oscillator (OPO); in 1965, Jotmeyer and Miller successfully produced the first OPO / OPA device. OPO / OPA devices can provide tunable coherent light sources from visible light to infrared bands and have been widely used in many fields of laser science and laser technology.

[0003] The working principle of the optical parametric oscillator-amplifier (OPO / OPA) device is to use the optical parametric interaction between a strong pump light source and a nonlinear optical crystal with a sufficiently large nonlinear response rate to obtain two new lasers with wavelengths greater than the wavelength of the incident pump light. In an optical parametric oscillator (OPO), the incident energy is The photons interact with the lattice of the nonlinear optical crystal and are inelastically scattered to produce two beams with energies of and The frequency of one of the laser beams is the laser frequency needed in the subsequent optical path, and this laser beam is called signal light; correspondingly, the other laser beam generated at the same time but not used by the subsequent optical path is called idler light. These lasers then enter the optical parametric amplifier (OPA), and after the same nonlinear optical process, the power density of the signal light is amplified twice, and finally reaches the power density required by the subsequent experiment.

[0004] Under actual experimental operating conditions, due to the different refractive indices of light of different wavelengths in nonlinear optical crystals, phase mismatch will occur among the pump light, signal light, and idler light, which will greatly reduce the energy conversion efficiency of the signal light generated by the OPO / OPA device. For the processes occurring in nonlinear optical crystals, angle phase matching is generally used to compensate for the dispersion effect in the crystal. Angle phase matching has certain requirements for the polarization directions of the pump light, signal light, and idler light. The following table lists the polarization direction requirements of the pump light, signal light, and idler light that meet the angle phase matching conditions when the nonlinear optical crystals are positive uniaxial crystals and negative uniaxial crystals, respectively.

[0005] Type I phase matching polarization characteristics Type II phase matching polarization characteristics Positive uniaxial crystal o→e+e o→o+e Negative uniaxial crystal e→o+o e→e+o

[0006] For a specific optical parametric interaction process, the polarization directions that the pump light, signal light, and idler light should satisfy are determined by the type of optical crystal and the wavelength range of the three laser beams. The optical parametric interaction process can only occur when the polarization directions of the three laser beams are strictly consistent with the above table, otherwise it cannot occur.

[0007] Since the materials and cutting angles of the nonlinear optical crystals used in the OPA device are exactly the same as those in the OPO, the OPA crystal not only meets the phase matching conditions of the optical parametric amplification process, but also meets the phase matching conditions of its inverse process (i.e., the process of signal light and idler light sum frequency as pump light). Therefore, in fact, the OPA crystal carries out both the optical parametric amplification process we need and its corresponding inverse process. The existence of this inverse process leads to a decrease in the signal light energy output by the OPA, which seriously limits the energy conversion efficiency of the OPA device. Therefore, weakening or even completely eliminating this inverse process has become a top priority to improve the energy utilization of the OPA device. Summary of the invention

[0008] In view of the shortcomings of the prior art, the OPA device has a problem of limited energy conversion efficiency due to the reverse process of optical parametric amplification. The present invention provides an experimental device that can improve the energy conversion efficiency of the optical parametric amplifier (OPA). The signal light and pump laser generated by the optical parametric oscillator undergo an optical parametric amplification process when entering the first nonlinear optical OPA crystal 1, generating signal light (signal) and idler light (idler). When these two wavelengths of laser light enter the second nonlinear optical OPA crystal 2, a reverse nonlinear optical process will occur to return to the pump light wavelength, thereby causing energy loss of the signal light and reducing the energy conversion efficiency of the OPA device. The 1 / 2 wave plate placed between the two OPA crystals changes the polarization direction of the pump light, signal light, and idler light, so that the signal light and idler light entering the second nonlinear optical OPA crystal 2 cannot undergo a reverse conversion process because they do not meet the phase matching conditions, thereby avoiding the signal light energy loss caused by the reverse sum frequency process and greatly improving the amplification efficiency of the OPA device.

[0009] The technical solution adopted by the present invention to achieve the above purpose is to add a 1 / 2 wave plate between two OPA crystals. The wavelength range of the wave plate includes the wavelength of the pump light and signal light incident on the OPA, but does not include the wavelength of the idle light. The technical solution of the present invention is as follows:

[0010] An OPA energy conversion efficiency improvement device comprises two nonlinear optical OPA crystals and a 1 / 2 wave plate, wherein the 1 / 2 wave plate is placed between a nonlinear optical OPA crystal 1 and a nonlinear optical OPA crystal 2 and is placed perpendicular to the laser propagation direction, and the distance between the 1 / 2 wave plate and the front and rear nonlinear optical OPA crystals 1 and 2 is equal, which is 1-3 cm.

[0011] Nonlinear optical OPA crystal 1 and nonlinear optical OPA crystal 2: They are important components of the optical parametric amplifier (OPA). When the low-energy signal light and high-energy pump light generated from the optical parametric oscillator (OPO) enter the OPA crystal, an optical parametric interaction process will occur, which plays a role in amplifying the signal light energy.

[0012] 1 / 2 wave plate: changes the polarization of the pump light and the signal light so that the pump light, the signal light and the idler light entering the nonlinear optical OPA crystal 2 cannot undergo the reverse process of the optical parametric interaction process because they do not meet the phase matching condition.

[0013] The principal optical axis directions of the nonlinear optical OPA crystal 1 and the nonlinear optical OPA crystal 2 are perpendicular to each other.

[0014] There are no optical elements between the 1 / 2 wave plate and the nonlinear optical OPA crystal 1 and the nonlinear optical OPA crystal 2.

[0015] The operating wavelength range of the 1 / 2 wave plate covers the wavelengths of pump light and signal light, but does not cover the wavelength of idle light.

[0016] The light incident surface and the light emitting surface of the 1 / 2 wave plate are both coated with anti-reflection films, and the wavelengths corresponding to the anti-reflection films cover the wavelengths of pump light and signal light, but do not cover the wavelengths of idle light.

[0017] Advantages of the present invention:

[0018] Compared with the prior art, the 1 / 2 wave plate placed between the two OPA crystals of the present invention changes the polarization direction of the pump light, signal light and idle light, so that the signal light and idle light entering the second nonlinear optical OPA crystal 2 cannot undergo a reverse conversion process because they do not meet the phase matching conditions, thereby avoiding the signal light energy loss caused by the reverse sum frequency process, and greatly improving the amplification efficiency of the OPA device. In addition, the present invention has high space utilization, and the design scheme provided by the present invention does not need to occupy any additional space. The present invention is simple to operate and easy to implement. If the design scheme of the present invention is adopted, the optical path modification of the original OPA device is small and the time consumption is short. Since the reverse conversion is suppressed, the laser emitted from the OPA is purer (the proportion of laser light of other wavelengths is small), which can avoid adding more other filter elements to the optical path, simplify the optical path, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of the present invention.

[0020] Among them, 1, 2: nonlinear optical OPA crystals; 3: 1 / 2 wave plate. DETAILED DESCRIPTION

[0021] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited by the embodiments. If technical personnel skilled in the art make some non-essential improvements and adjustments to the present invention based on the above invention content, they still fall within the protection scope of the present invention.

[0022] Example 1

[0023] The present embodiment provides an OPA energy conversion efficiency improvement device, which includes two nonlinear optical OPA crystals and a 1 / 2 wave plate, wherein the 1 / 2 wave plate is placed between the nonlinear optical OPA crystal 1 and the nonlinear optical OPA crystal 2, and is placed perpendicular to the laser propagation direction, and the distance between the 1 / 2 wave plate and the front and rear nonlinear optical OPA crystals 1 and the nonlinear optical OPA crystal 2 is equal, which is 1-3 cm.

[0024] Nonlinear optical OPA crystal 1 and nonlinear optical OPA crystal 2: They are important components of the optical parametric amplifier (OPA). When the low-energy signal light and high-energy pump light generated from the optical parametric oscillator (OPO) enter the OPA crystal, an optical parametric interaction process will occur, which plays a role in amplifying the signal light energy.

[0025] 1 / 2 wave plate: changes the polarization of the pump light and the signal light so that the pump light, the signal light and the idler light entering the nonlinear optical OPA crystal 2 cannot undergo the reverse process of the optical parametric interaction process because they do not meet the phase matching condition.

[0026] The principal optical axis directions of the nonlinear optical OPA crystal 1 and the nonlinear optical OPA crystal 2 are perpendicular to each other.

[0027] There are no optical elements between the 1 / 2 wave plate and the nonlinear optical OPA crystal 1 and the nonlinear optical OPA crystal 2.

[0028] The operating wavelength range of the 1 / 2 wave plate covers the wavelengths of pump light and signal light, but does not cover the wavelength of idle light.

[0029] The light incident surface and the light emitting surface of the 1 / 2 wave plate are both coated with anti-reflection films, and the wavelengths corresponding to the anti-reflection films cover the wavelengths of pump light and signal light, but do not cover the wavelengths of idle light.

[0030] Example 2

[0031] This embodiment provides an OPA energy conversion efficiency improvement device, and the polarization directions of the pump light, signal light and idle light emitted from the nonlinear optical OPA crystal 1 meet the angular phase matching requirements corresponding to the crystal.

[0032] This embodiment takes the type I matching process of a negative uniaxial crystal as an example: the polarization direction of the incident nonlinear optical OPA crystal 1 pump light should be o light (ordinary light), and the outgoing signal light and idle light are both e light (extraordinary light). After passing through the polarizer, the polarization directions of the pump light and signal light are deflected by 90°. Although the wavelength of the idle light is not within the range of the wave plate, it is still deflected by an angle of θ (0°

Claims

1. An OPA energy conversion efficiency improvement device, characterized in that: The OPA energy conversion efficiency improvement device comprises two nonlinear optical OPA crystals and a half-wave plate, wherein the half-wave plate is placed between the nonlinear optical OPA crystal (1) and the nonlinear optical OPA crystal (2) and is placed perpendicular to the laser propagation direction; the main optical axis directions of the nonlinear optical OPA crystal (1) and the nonlinear optical OPA crystal (2) are perpendicular to each other; The distance between the 1 / 2 wave plate and the front and rear nonlinear optical OPA crystals (1) and the nonlinear optical OPA crystal (2) is equal, which is 1-3 cm; There are no optical elements between the 1 / 2 wave plate and the nonlinear optical OPA crystal (1) and the nonlinear optical OPA crystal (2); the action wavelength range of the 1 / 2 wave plate covers the wavelengths of pump light and signal light, but does not cover the wavelength of idle light; The light incident surface and the light emitting surface of the 1 / 2 wave plate are both coated with anti-reflection films, and the wavelengths corresponding to the anti-reflection films cover the wavelengths of pump light and signal light, but do not cover the wavelengths of idle light.

Images