JP2752320B2 - Optical parametric oscillator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical parametric oscillator, and more particularly to an optical parametric oscillator suitable for achieving high conversion efficiency and obtaining a large oscillation output.

[0002]

2. Description of the Related Art At present, most lasers on the market are:
Laser oscillation at a specific oscillation line is obtained, that is, a laser of a fixed wavelength. Lasers with such various fixed wavelengths are applied in various fields, but if the laser light can be changed in frequency freely like radio waves used for communication, etc. Significant progress can be expected in applications. Based on such expectations, tunable lasers have been developed since the early days when laser oscillation was confirmed.

As a wavelength variable laser, there is a dye laser, a laser utilizing a non-linear effect and stimulated Raman scattering. Optical parametric oscillators, utilizes the optical parametric effect, sell laser oscillation frequency omega _s of the signal light (signal light) and the idler light frequency omega _i by the frequency omega _p of the pumping light (pump light) to a nonlinear crystal (Ω _p = ω _s + ω _i ). This laser is continuously tunable and is known to be effective in picosecond pulse operation. Then, for example, “Japanese Unexamined Patent Application Publication No.
694 "shows a fully automatic wavelength tunable laser controlled by a computer.

In the conventional optical parametric oscillator, the wavelength of the pump light source is fixed, and when the wavelengths of the required signal light and idler light are determined, the phase matching condition is determined from these conditions. Even if the wavelength of the excitation light source is variable,
After fixing the wavelength of the pump light source, the phase matching condition is determined.

Further, in order to operate the optical parametric oscillator in the femtosecond region, an optical parametric oscillator called Opal manufactured by Spectra Physics uses a tunable femtosecond titanium sapphire laser as an excitation light source and uses the femtosecond pulse repetition frequency and Forced mode locking is achieved by completely synchronizing the frequency of the optical parametric oscillator. Therefore, the resonator length is controlled with very high precision, and the femtosecond operation is performed only by this control. Then, in order to achieve a shorter time width, a prism pair is inserted inside the optical parametric oscillator for dispersion correction.

[0006]

When the optical parametric oscillator is pulsed, if the time width of the signal light and the idler light propagating inside the resonator is less than picosecond, ideal optical parametric amplification cannot be performed. There is a problem. FIG. 11 schematically illustrates this. When the pump light P _P , the signal light P _S , and the idler light P _I enter the nonlinear crystal 110, the signal light P _S from the nonlinear crystal 110 due to the wavelength dispersion characteristics. illustrates how the idler light P _I time tau ₁ to the pump light P _P, is tau ₂ delayed output. Due to the wavelength dispersion characteristics of the material forming the resonator, a difference in group velocity occurs between pump light or signal light having different wavelengths and idler light. For this reason, a phase shift occurs between these light pulses inside the resonator (this phenomenon is usually called walk-off).

In order to avoid the influence, for example, in US Pat. No. 5,017,806, group delay occurring in a nonlinear crystal is suppressed by reducing the thickness of the crystal, and the phase shift between light pulses is reduced. . However, because the nonlinear crystal obtains pump light and signal light by the optical parametric effect as described above, the walk-off may be small,
Conversion efficiency will be reduced. The thickness of the nonlinear crystal is
Not only does it determine the walk-off, it also determines the conversion efficiency. Therefore, there is a problem that the nonlinear crystal cannot be thinned unnecessarily.

In order to increase the conversion efficiency by reducing the thickness of the nonlinear crystal, it is necessary to collect the excitation light using a lens having a short focal length. However, in this case, there is a problem that signal light having different wavelengths and idler light are mixed due to the phase matching condition, and monochromatic light cannot be obtained.

[0009]

In order to solve the above problems, an optical parametric oscillator according to the present invention includes a wavelength tunable mechanism for variably changing the wavelength of pump light, and a pump for outputting a pulse of variable wavelength pump light. A light source, a nonlinear medium that oscillates optically parametrically by irradiating the excitation light, emits signal light and idler light, a nonlinear medium is arranged, and a phase matching adjustment mechanism that adjusts a phase matching condition of the nonlinear medium is sandwiched between the nonlinear medium. And a wavelength tunable mechanism based on the correlation between the wavelength of the required signal light or idler light and the dispersion characteristic of the nonlinear medium, and an optical system that forms a resonator for the signal light, idler light, and pump light. And a control means for simultaneously controlling the phase matching adjustment mechanism and adjusting the wavelength of the excitation light and the phase matching condition of the nonlinear medium with respect to the excitation light.

The phase matching adjustment mechanism adjusts a phase matching condition by changing at least one of an incident angle of the pump light to the nonlinear medium, a temperature of the nonlinear medium, and a voltage applied to the nonlinear medium. It may be a feature.

The pumping light source includes a laser oscillator, and the variable wavelength mechanism includes a birefringent filter disposed in a laser cavity of the laser oscillator. The variable wavelength mechanism rotates the birefringent filter. The wavelength of the excitation light may be made variable by using this.

The wavelength variable mechanism has a first gear mechanism for rotating the birefringent filter, the phase matching adjustment mechanism has a second gear mechanism for changing the angle of incidence of the excitation light on the nonlinear medium, The control means has a third gear mechanism that meshes with the first and second gear mechanisms, and simultaneously rotates the birefringent filter and the non-linear medium with the third gear mechanism to control the wavelength and phase matching of the excitation light. It may be characterized in that conditions are adjusted simultaneously.

[0013]

In the optical parametric oscillator according to the present invention, the non-linear medium oscillates optically parametrically by irradiating the excitation light pulse, thereby generating a pulse of the signal light and a pulse of the idler light. These lights are laser-oscillated by signal light, idler light and pumping light by an optical system constituting a resonator. Here, the wavelength variable mechanism and the phase matching adjustment mechanism are simultaneously controlled based on the correlation between the required signal light or idler light wavelength and the dispersion characteristic of the nonlinear medium. Therefore, the signal light, the idler light, and the pumping light can be adjusted to the optimum value so that the difference in time for propagating through the nonlinear medium is minimized, and the phase matching condition of the nonlinear medium with respect to the pumping light can be adjusted to the optimum value. Therefore, the timing of the laser pulses of the signal light, the idler light, and the pump light in the resonator can be made uniform, and the intensity of the pump light propagating through the nonlinear medium can be increased. Therefore, the efficiency with which necessary signal light or idler light is generated can be increased.

[0014]

An embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a conceptual diagram of the configuration of the present invention.

An excitation light source 1 of this optical parametric oscillator
The 30, used wavelength such titanium sapphire laser is tunable pulsed light source, the optical path of the excitation light P _P from the excitation light source 130, opposed mirrors M1, M2 by the resonator is disposed. In this resonator, pump light P _P
Optical parametric conversion is performed by the irradiation of the nonlinear optical crystal 1 to generate a signal light P _S and idler light P _I
10 are arranged. The mirror M1 is connected to the excitation light source 130.
Transmitting excitation light P _P from but adapted to reflect the pumping light P _P, the signal light P _S and idler light P _I to the excitation light source 130 from the nonlinear optical crystal 110. Mirror M2
It is totally reflected excitation light P _P from the nonlinear optical crystal 110, and transmit a portion partially reflected signal light P _S and idler light P _I. The pump light P _P , the signal light P _S and the idler light P _I are confined by this resonator,
It oscillates.

As the nonlinear optical crystal 110, a beta barium baud rate or the like can be used. The nonlinear optical crystal 110 is mounted on a stage 115. The stage 115 is rotatable and has a built-in heater and electrodes for applying a voltage to the nonlinear optical crystal 110.
By a control signal from the computer 310, or change the incident angle of the excitation light P _P to the non-linear optical crystal 110, or a nonlinear optical crystal 1 by heating the nonlinear optical crystal 110
10 and the voltage applied to the nonlinear optical crystal 110 can be changed.

[0017] Between the excitation light source 130 and the mirror M1 half mirror M5 are arranged, part of the excitation light P _P from the excitation light source 130 is made incident to the spectroscope 410. The spectroscope 410 detects the wavelength of the excitation light P _P and outputs a detection signal corresponding to the wavelength to the computer 310. The computer 310 determines whether the wavelength of the excitation light P _P is the determined wavelength from the detection signal, and sends the excitation light P to the excitation light source 130 so that the wavelength of the excitation light P _P becomes the determined wavelength. Outputs a signal for controlling the wavelength of _P.

On the optical path of the signal light P _S and the idler light P _I having exited from the resonator from the mirror M2, the signal light P
Half mirrors M3 and M4 that reflect a part of _S (or idler light P _I ) are arranged. Half mirror M
The signal light P _s (or the idler light P _I ) reflected by M3 and M4 respectively enters the spectroscope 420 and the power meter 430. The spectroscope 420 has the signal light P _S
(Or the idler light P _I ), and outputs a detection signal corresponding to the wavelength to the computer 310. The power meter 430 detects the intensity of the signal light P _S (or the idler light P _I ), and outputs a detection signal corresponding to the intensity to the computer 310.

The computer 310 transmits the necessary signal light P _S
Is input from the outside, and the given signal light P _S
The wavelength of the original, as well as determining the wavelength of the excitation light P _P, obtains a phase matching condition of the nonlinear optical crystal 110 for the excitation light P _P of the determined wavelength, the nonlinear optical crystal sends a signal to the stage 115 110 controls so as to satisfy this phase matching condition. Then, detection signals from the spectrometer 410, the spectrometer 420, and the power meter 430 are input, the state of the apparatus is monitored, and a control signal is sent to control the apparatus to an optimum state.

FIG. 2 is a flowchart showing the operation of the apparatus.

[0021] First, when the input wavelength of the signal light P _S to the computer 310, computer 310, the wavelengths and the wavelength of the excitation light P _P based on the wavelength of the input signal light P _S with respect to the excitation light P _P A phase matching condition of the nonlinear optical crystal 110 is obtained. Computer 310 determines the wavelength of the excitation light P _P, the signal light P _S and the pumping light P _P as idler light P _I is reduced so as to be, respectively substantially the difference between the time of propagation inside the nonlinear optical crystal 110 . The wavelength of the excitation light P _P is obtained from the group delay characteristics of the nonlinear optical crystal 110.

FIG. 3 shows that the nonlinear optical crystal 110 has a thickness of 1 m.
m beta barium baud rate,
Pumping light P _P with respect to the signal light P _S and idler light P _I pumping light P _P such as the difference between the delay time of the nonlinear optical crystal 110 becomes zero, the wavelength of the signal light P _S and idler light P _I It shows the relationship. The computer 310 is such a relationship is previously input, the computer 310 by using this relationship determine the wavelength of the excitation light P _P from the wavelength of the signal light P _S. When the relationship of FIG. 3 is used, if the wavelength of the necessary signal light P _S is about 1.53 μm, the wavelength of the pump light P _P becomes 700 nm. If the wavelength of the necessary signal light P _S is about 1.87 μm, the wavelength of the pump light P _P becomes 900 nm. Since the oscillation wavelength of the Ti: sapphire laser is 700 to 900 nm, the excitation light source 13 to the wavelength of the excitation light P _P determined by the computer 310
By adjusting the wavelength of 0, so that the signal light P _S having a wavelength required (1.53~1.87μm) is obtained.

The phase matching conditions of the nonlinear optical crystal 110 is changed by the wavelength of the pumping light P _P, but if the wavelength of the excitation light P _P is determined, the phase matching of the nonlinear optical crystal 110 for the excitation light P _P of the wavelength The conditions are fixed. That is, the incident angle of the excitation light P _P to nonlinear optical crystal 110 satisfying the phase matching condition is determined. Since different angles of incidence the voltage applied to the temperature and the nonlinear optical crystal 110 of the nonlinear optical crystal 110 for the excitation light P _P, also the relationship between the computer 310 and these temperature and voltage to the incident angle of the excitation light P _P The computer 310 controls the temperature of the nonlinear optical crystal 110 and the voltage applied to the nonlinear optical crystal 110 such that the phase matching condition is satisfied.

The signal light P _S (or the idler light P _I ) obtained by the parametric oscillation of the nonlinear optical crystal 110
Is measured by the spectroscope 420, its intensity is measured by the power meter 430, and monitored by the computer 310. Then, the computer 31 is set so that the signal light P _S has the required intensity with the required wavelength accuracy.
If the value is 0, the measured value is compared with a set value and fed back to perform a minute correction. Then, after fine-tuning the entire oscillator so that the nonlinear optical crystal 110 satisfies the phase matching condition, the setting ends. Thus, the oscillation wavelength finally set is obtained.

Thus, from the wavelength of the required signal light P _S ,
Setting the state of the nonlinear optical crystal 110 so as to satisfy the phase matching condition of the nonlinear optical crystal 110 for the excitation light P _P of the wavelength at the same time to determine the wavelength of the excitation light P _P such that the difference between the delay time is zero As a result, the group velocity matching condition and the phase matching condition are satisfied at the same time, the timings of the laser pulses of the signal light P _S , the idler light P _I, and the pump light P _{P in} the resonator can be aligned, and the propagation of the nonlinear medium The intensity of the excited excitation light can be increased. Therefore, it is possible that can increase the generation efficiency of the necessary signal light P _S or idler light P _I.

FIG. 4 schematically shows this, and it can be considered that the steady state of the resonator is schematically shown. In the state shown in this figure, the group velocity matching condition and the phase matching condition are satisfied at the same time, and the nonlinearity is set in the resonator 119 so that there is no group delay between the signal light P _S , the idler light P _I, and the pump light P _P. The phase matching conditions such as the angle of the optical crystal 110, the signal light P _S , the idler light P _I, and the pump light P
The wavelength of _P is limited. Since there is no group delay in these optical signal light P _S, idler light P _I and the excitation light P
_P simultaneously exits the nonlinear optical crystal 110 and the mirrors M1,
After being reflected by M2, it returns to the nonlinear optical crystal 110 at the same time. Also, is the most one intensity is greater pumping light P _P exiting from the nonlinear optical crystal 110 from the fact that the phase matching condition is satisfied at the same time. Therefore, it is possible that can increase the generation efficiency of the signal light P _S or idler light P _I.

FIG. 5 shows the result of simulating the delay time of the pulse of the signal light P _S and the pulse of the idler light P _I with respect to the pulse of the pump light P _P generated during one round inside the resonator. With beta barium baud rate as the nonlinear optical crystal 110, and a 600nm wavelength of the excitation light P _P. The excitation light P _P is incident at a phase matching angle with respect to refractive errors, the signal light P _S, the idler light P _I is assumed to have a deflection characteristic of the ordinary refractive index axis direction.

Normally, an optical crystal has a dispersion characteristic that the propagation speed varies depending on the wavelength of light.
As is clear from the above, when the wavelength of the signal light P _S and the idler light P _I is about 1.1 μm, the group delay of the signal light P _S and the idler light P _I with respect to the pump light P _P becomes zero. That is, 1.1 μm for the excitation light P _{P having} a wavelength of 600 nm.
The signal light P _s and the idler light P ₁ of the same degree have the same group velocity and propagate through the crystal at the same time. The present invention achieves optical parametric oscillation with high conversion efficiency without walk-off by selectively oscillating the optical parametric oscillator at such a wavelength.

The operation without the walk-off is based on the pump light P
Is determined by parameters such as the temperature of the matching angle and a nonlinear optical crystal 110 of _P wavelengths and a non-linear optical crystal 110, a nonlinear optical crystal in the wavelength and the wavelength of the excitation light P _P corresponding to the necessary signal light P _S 110 Can be obtained by calculation. In addition, the thickness of the nonlinear optical crystal 110 is not particularly affected by the operation without walk-off (however, if the crystal becomes thicker, the pulse width may be broadened due to chromatic dispersion. May be easier). In reality, it is necessary to consider the non-uniformity of the crystal and the like, so it is considered preferable to use an appropriate thickness. FIG. 3 shows a signal light P _S or an idler light P _I required for an operation without walk-off from the above-mentioned viewpoint.
In which to determine the relationship between the wavelength and the wavelength of the excitation light P _P for generating these. By inputting the group velocity-matched relationship as shown in FIG. 3 to a computer in advance, optical parametric oscillation with high conversion efficiency without walk-off is achieved.

As described above, according to the present invention, even if the pulse operation optical parametric oscillator has a dispersion characteristic inside the resonator, the pumping light P _P and the signal light P _S, can provide a group delay is not resonator between idler light P _I. Therefore, the thickness of the nonlinear optical crystal can be increased, so that an optical parametric oscillator with high conversion efficiency can be provided.

FIG. 6 shows a more detailed configuration. In the following, the description of the same or equivalent components as described above will be simplified or omitted.

[0032] The optical parametric oscillator, the resonator on the optical path of the excitation light P _P from the excitation light source 130 by mirrors M1, M2 are disposed, the nonlinear optical crystal 110 is disposed in the resonator. Nonlinear optical crystal 110 is placed on the stage 115, or changing the incident angle of the excitation light P _P to the non-linear optical crystal 110, or changing the temperature of the nonlinear optical crystal 110 by heating the nonlinear optical crystal 110, a nonlinear The voltage applied to the optical crystal 110 can be changed. Then, a half mirror M5 is arranged between the excitation light source 130 and the mirror M1, and the spectroscope 4
And it detects the wavelength of the excitation light P _P 10.
Further, a half mirror M3 on the optical path of the signal light P _S and idler light P _I emitted to the outside of the cavity from the mirror M2, M4
Is arranged, and the spectroscope 420 and the power meter 430 detect the wavelength and the intensity of the signal light P _S (or the idler light P _I ). Up to this point, the operation is the same as in the above-described embodiment.

As the excitation light source 130, a pulse light source having a variable wavelength such as a titanium sapphire laser is used.
Rotatable on the optical path of the excitation light P _P birefringent filter 13
2 is provided, so that the wavelength of the excitation light P _P is varied in accordance with the rotation angle. Computer 310
Is the wavelength of the necessary signal light P _S is input from the outside, based on the wavelength of the given signal light P _S, as well as determining the wavelength of the excitation light P _P, the excitation light of the determined wavelength P
The phase matching condition of the nonlinear optical crystal 110 with respect to _P is determined. Although available in this respect is similar to the above embodiment, the computer 310 is arranged to output a signal corresponding to the wavelength and the phase matching condition of the pumping light P _P to the controller 390.

The control device 390, the angle of the birefringent filter 132 by a signal from the computer 310, the incident angle of the excitation light P _P to the non-linear optical crystal 110, the temperature of the nonlinear optical crystal 110, the applied voltage are changed at the same time, Control these. That is, the control device 390 controls the computer 31
In response to a signal from 0 changing the phase matching condition of the wavelength and a non-linear optical crystal 110 of the pumping light P _P simultaneously and controls it.

FIG. 7 shows that the controller 390 determines the angle of the birefringent filter 132 and the excitation light P _P to the nonlinear optical crystal 110.
And FIG. 7 shows an example of a configuration in which the incident angles are controlled simultaneously. The birefringent filter 132 is provided with a gear 393 for rotating it, and the stage 115 of the nonlinear optical crystal 110 is also provided with a gear for rotating it. These gears are
0 is engaged with the gear 394 in the
The initial setting position and the gear ratio of the gear 3 and the gear of the stage 115 are determined so as to satisfy the relationship shown in FIG.
When the gear 394 rotates, the birefringent filter 13
2 and the stage 115 is rotated, the excitation light P into the nonlinear optical crystal 110 as a wavelength of the pumping light P _P so as to satisfy the relation is changed as shown in FIG. 3, satisfying the phase matching condition at the same time
The incident angle of _P changes. Thus, the control device 39
0 is an excitation light P according to a signal from the computer 310.
Control is performed by simultaneously changing the wavelength of _P and the phase matching condition of the nonlinear optical crystal 110.

FIG. 8 is a flowchart showing the operation of the apparatus.

[0037] First, when the input wavelength of the signal light P _S to the computer 310, computer 310, the excitation light P _P wavelengths and the wavelength of the excitation light P _P based on the wavelength of the signal light P _S inputted simultaneously Is determined for the nonlinear optical crystal 110 with respect to
90. The control device 390 starts the operation accordingly and rotates the gear 394 to control the birefringent filter 13.
By changing the temperature of the nonlinear optical crystal 110 and the applied voltage by simultaneously moving the angle 2 and the angle of the nonlinear optical crystal 110, the nonlinear optical crystal 110 is controlled to satisfy the phase matching condition.

[0038] By the above-described mechanism, the wavelength of the excitation light P _P and the phase matching conditions of the nonlinear optical crystal 110 is changed at the same time,
The wavelength is measured by the spectroscope 420, the intensity is measured by the power meter 430, and the control device 390
Is monitored. Then, the control device 390 outputs the signal light P
The measured value is compared with a set value and fed back to make a small correction so that _S has the required intensity with the required wavelength accuracy. Then, the control device 390 controls the nonlinear optical crystal 1
After fine-tuning the entire oscillator so that 10 satisfies the phase matching condition, the setting ends. Thus, the oscillation wavelength finally set is obtained.

[0039] In this way, by controlling the phase matching condition of the wavelength and a non-linear optical crystal 110 of the pumping light P _P simultaneously, the generation efficiency of rapidly necessary signal light P _S or idler light P _I Takashi It is possible to get.

[0040] Figure 9, the control unit 390, the excitation light P _P to an angle and a non-linear optical crystal 110 of the birefringent filter 132
This is another example of a configuration in which the incident angle is controlled simultaneously. Instead of the gear 394 in FIG.
93 is driven by a motor 392 via a gear 397,
The gear of the stage 115 is driven by a motor 395 via a gear 396. Motor 392,
The control unit 395 operates in synchronization with the control circuit 391 of the control unit 390. For example, a step motor or the like can be used for these units. And the motors 392 and 3
The rotation speed and gear ratio of 95 are set so as to satisfy the group speed and the phase matching condition. Thus, the operation is performed in the same manner as in the above embodiment.

FIG. 10 shows another configuration example in which the control device 390 simultaneously controls the angle of the birefringent filter 132 and the temperature (or applied voltage) of the nonlinear optical crystal 110. The non-linear optical crystal 110 is heated by a heater provided on the stage 115 instead of the drive system of the stage 115 in FIG. Motor 39
2, the driving of the birefringent filter 132 and the heating of the nonlinear optical crystal 110 by the heater are simultaneously performed by the control circuit 391 of the control device 390. The wavelength of the excitation light source 130 is controlled by a motor control signal from the control circuit 391 to the motor 392, and the nonlinear optical crystal 11
The temperature of 0 is controlled by the drive current to the heater of the stage 115, and these are controlled synchronously. As a result, the operation is performed so as to satisfy the group velocity and the phase matching condition as in the above embodiment.

When controlling the voltage applied to the nonlinear optical crystal 110, an electrode is provided on the nonlinear optical crystal 110 in place of the heater of the stage 115, and the voltage applied to this electrode is changed in the same manner.

[0043]

As described above, according to the present invention, the wavelength of the pump light and the phase matching of the nonlinear medium with respect to the pump light are determined based on the correlation between the wavelength of the required signal light or idler light and the dispersion characteristics of the nonlinear medium. Since the conditions are simultaneously adjusted to the optimum value, the timing of the laser pulse of the signal light or the idler light can be made uniform while increasing the intensity of the excitation light. Therefore, photons of signal light, idler light, or excitation light generated inside the nonlinear medium return to the inside of the nonlinear medium at the same time, so that the efficiency of generating signal light or idler light inside the nonlinear medium can be increased.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of the configuration of the present invention.

FIG. 2 is a diagram showing the operation of the apparatus of FIG.

[3] the pumping light P _P with respect to the signal light P _S and idler light P _I pumping light P _P such as the difference between the delay time of the nonlinear optical crystal 110 becomes zero, the signal light P _S and idler light P
_The figure which showed the relationship of the wavelength of _I.

FIG. 4 is a diagram schematically showing the operation of the apparatus shown in FIG. 1;

FIG. 5 is a diagram showing a result of simulation of pulse delay times of the signal light P _S and the idler light P _I.

FIG. 6 is a configuration diagram of a more detailed embodiment.

FIG. 7 is a diagram showing a configuration example of a control device.

FIG. 8 is a diagram showing the operation of the device of FIG. 6;

FIG. 9 is a diagram showing a modification of the control device.

FIG. 10 is a diagram showing a modification of the control device.

FIG. 11 is a view showing a walk-off.

[Explanation of symbols]

110: nonlinear crystal, 115: stage, 119: resonator, 130: excitation light source, 132: filter, 310: computer, 390: control device, 391: control circuit, 3
93,394,396,397 ... gear, 392,395
... Motors, M1 to M5 ... Mirrors.

Claims (4)

(57) [Claims] An excitation light source for outputting a pulse of excitation light having a variable wavelength; a light source for outputting a pulse of excitation light having a variable wavelength; and an optical parametric conversion by irradiating the excitation light to convert signal light and idler light. A nonlinear medium that emits, the nonlinear medium is disposed, a phase matching adjustment mechanism that adjusts a phase matching condition of the nonlinear medium, and the signal light is disposed so as to sandwich the nonlinear medium.
An optical system forming a resonator for the idler light and the pumping light, and a wavelength variable mechanism based on a correlation between a required wavelength of the signal light or the idler light and a dispersion characteristic of the nonlinear medium. An optical parametric oscillator comprising: control means for simultaneously controlling the phase matching adjustment mechanism and adjusting a wavelength of the pump light and a phase matching condition of the nonlinear medium with respect to the pump light. 2. The phase matching adjusting mechanism changes the phase by changing at least one of an incident angle of the pumping light to the nonlinear medium, a temperature of the nonlinear medium, and a voltage applied to the nonlinear medium. The optical parametric oscillator according to claim 1, wherein a matching condition is adjusted. 3. The pumping light source includes a laser oscillator. The wavelength tunable mechanism includes a birefringent filter disposed in a laser cavity of the laser oscillator. 2. The optical parametric oscillator according to claim 1, wherein the wavelength of the excitation light is made variable by rotating a refraction filter. 4. The wavelength variable mechanism has a first gear mechanism for rotating the birefringent filter, and the phase matching adjustment mechanism is configured to change an incident angle of the excitation light to the nonlinear medium. The control means includes a third gear mechanism that meshes with the first and second gear mechanisms, and the third gear mechanism simultaneously controls the birefringent filter and the nonlinear medium. The optical parametric oscillator according to claim 3, wherein the wavelength of the pump light and the phase matching condition are simultaneously adjusted by rotating the optical parametric oscillator.