JPH09186386A - Laser resonator and laser provided therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a laser which is possessed of frequency characteristics such as small phase shift and surely and stably controlled in cavity length in a wide servo frequency band of tens of kHz. SOLUTION: An electromagnetic actuator is equipped with a moving part 41 composed of a cylindrical coil bobbin 31 provided with a coil 32 wound on its periphery in a solenoid and a ring-shaped member 33 which is formed of metal such as copper (Cu) or gold (Au) low in electrical resistance and where the coil bobbin 31 is fitted in and fixed so as to surround the coil 32. A yoke 35 which is formed of ferromagnetic material and provided with a permanent magnet 34 that is magnetized as prescribed and located at its inner circumference is provided, and the moving part 41 is disposed in the yoke 35.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser resonator for wavelength-converting incident laser light and emitting the laser light, and a laser light generator using the same.

[0002]

2. Description of the Related Art Recently, a nonlinear optical crystal element has been arranged in a laser resonator for wavelength-converting incident laser light to emit the laser light, and the high power density inside the laser resonator is utilized to efficiently perform nonlinearity. A laser light generator that performs wavelength conversion using an optical crystal element has been proposed.

As such a laser beam generator, there is, for example, an external resonator type second harmonic wave generator (SHG).

In this external resonator type SHG, a nonlinear optical crystal element is arranged between a pair of reflecting mirrors constituting the external resonator, and a laser beam having a fundamental wavelength is made incident on this external resonator. Pass through a non-linear optical crystal element.
In this case, the external resonator is the frequency (wavelength) of the incident laser light.
The length (resonator length) that resonates with is selected.

This external resonator type SHG has a so-called finesse value (value corresponding to the Q value of resonance) of 100 to, for example.
The nonlinear effect of the nonlinear optical crystal element provided in the external resonator is utilized by increasing the optical density inside the external resonator by several thousand times to make the optical density inside the external resonator several hundred times.

By the way, in the case of obtaining the second harmonic laser light and the laser light of higher order high frequency and sum frequency by wavelength conversion by the laser resonator, the change (error) of the optical path length in the laser resonator is caused. ) Is 1/10 of the resonance wavelength
It is required to control in an extremely fine range from 00 to 1/10000, that is, 1 angstrom or less,
Extremely accurate position control is required.

Therefore, conventionally, for example, a laminated piezoelectric element (PZT) is used as a moving means for supporting and moving a reflecting mirror which is a component of a laser resonator. This laminated piezoelectric element enables fine adjustment of the movement of the reflecting mirror in the optical axis direction, and an error signal proportional to the deviation of the resonator length of the laser resonator with respect to the incident laser light is fed back to the laminated piezoelectric element to cause the servo loop to operate. Composed. This servo loop automatically controls the resonator length to stabilize the resonance operation of the laser resonator with respect to the incident laser light.

[0008]

However, the above-mentioned laminated piezoelectric element generally has multiple resonance (structural resonance) of several kHz to several tens of kHz, and due to the self-capacitance of the laminated piezoelectric element, the whole frequency range is increased. Therefore, a phase delay easily occurs.

Therefore, when the laminated piezoelectric element is used as the moving means of the reflecting mirror which is a component of the laser resonator as described above, it is difficult to extend the servo band to a region of several tens kHz.

Further, the above-mentioned laminated piezoelectric element has a very high driving voltage of several hundreds to several thousands of volts, which requires an extremely complicated and expensive driving electric circuit.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to control the resonator length in a stable and reliable manner in a wide servo band of several tens of kHz with a small frequency characteristic around the phase. It is to provide a laser resonator capable of performing the above and a laser light generator using the same.

[0012]

The object of the present invention is to provide at least a pair of reflecting means, and a nonlinear optical crystal element disposed between the reflecting means, and to enter the nonlinear optical crystal element. It is a laser resonator that generates wavelength-converted laser light by resonating the laser light.

In the laser resonator of the present invention, at least one of the reflecting means is fitted and fixed in a cylindrical coil bobbin having a coil wound around the outer periphery thereof, and is made of a metal material having a low electric resistance value. The reflecting means is arranged in an annular yoke made of a ferromagnetic material via a cylindrical plate, and the reflecting means is moved by electromagnetic induction by supplying a driving current to the coil.

Specifically, it is preferable to use copper or gold as a metal material having a low electric resistance value which is a material of the cylindrical plate.

Further, the object of the present invention is to provide a laser light source for emitting a laser beam having a fundamental wavelength and at least a pair of reflecting means, and a nonlinear optical crystal element arranged between the reflecting means to provide the above laser. A laser light generator comprising: a laser resonator that generates a wavelength-converted laser light by resonating a laser light that has entered the nonlinear optical crystal element from a light source.

Here, the moving means is configured as the electromagnetic actuator described above. Further, it is preferable to use copper or gold as a metal material having a low electric resistance value which is a material of the cylindrical plate.

In the laser resonator according to the present invention, an electromagnetic induction action occurs because the magnetic circuit is a closed magnetic circuit even though no conductor or magnetic material typified by metal is arranged inside the coil. Gives a large thrust.

At this time, since the cylindrical plate made of a metal material having a low electric resistance value is provided between the coil and the permanent magnet, generation of eddy currents on the coil surface and the permanent magnet surface is suppressed, It is possible to realize a transfer characteristic with less phase shift.

By mounting this laser resonator on a laser light generator having a laser light source, it becomes possible to stably and reliably emit laser light having a desired resonance frequency.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments in which the laser resonator of the present invention is applied to a laser light generator will be described in detail below with reference to the drawings.

As shown in FIG. 1, the laser beam generator according to this embodiment resonates the laser beam emitting means 1 for emitting a laser beam and the incident laser beam from the laser beam emitting means 1. A laser resonator 2 for generating a wavelength-converted laser beam, and the laser resonator 2
And a control means 3 for servo-controlling the resonator length.

The laser light emitting means 1 includes a laser light source 11 for emitting an incident laser light having a fundamental wavelength, and a laser resonator 2.
A phase modulator 12 that performs phase modulation on the incident laser light to
A semi-transmissive mirror 13 that is a dichroic mirror that almost completely totally reflects a laser beam having a predetermined wavelength, for example, a wavelength of 266 nm, and a condenser lens 14 that condenses the laser beam that has passed through the mirror 13. Has been done.

Here, the laser light source 11 has, for example, a wavelength of 5
It emits green laser light of 32 nm, and as the phase modulator 12, for example, an EO (electro-optic) element or an AO (acousto-optic) element is used.

The laser resonator 2 is a pair of reflecting mirrors 15 and 16 that are opposed to each other with the optical axis as a central portion and serve as reflecting means.
A non-linear optical crystal element 17 arranged at a predetermined position between the reflecting mirrors 15 and 16, and an electromagnetic actuator 18 which is a moving means for moving the reflecting mirror 15 in the optical axis direction to control the resonator length. It consists of

In the pair of reflecting mirrors 15 and 16, the reflecting mirror 15 is a plane mirror and the reflecting mirror 16 is a concave mirror.

Further, as the nonlinear optical crystal element 17,
For example, KTiOPO ₄ (KTP), LiNbO ₃ (L
N), quasi phase matching LN (QPMLN), β-BaB ₂
O ₄ (BBO), KNbO ₃ (KN) or the like is used.

And, in particular, the electromagnetic actuator 18 is
A so-called voice coil motor is provided with at least one coil, a permanent magnet, and a yoke made of a magnetic material.

Specifically, this electromagnetic actuator 18
2 to 5, the coil bobbin 31 has a cylindrical shape in which a coil 32 is wound around the outer periphery in a solenoid shape, and the coil bobbin 31 is fitted and fixed so as to surround the coil 32. The permanent magnet 34 is provided with a moving portion 41 including a cylindrical plate 33 made of a metal material having a low electric resistance value such as copper (Cu) or gold (Au) and having a predetermined magnetized inner peripheral portion. Has a yoke 35 made of a ferromagnetic material such as iron.
1 is allocated.

Here, the permanent magnet 34 is magnetized so that, for example, the inner peripheral side has an N pole and the outer peripheral side has an S pole.

Further, a pair of leaf springs 42 and 43, on which the moving portion 41 is supported and fixed at the upper and lower portions thereof, and a ferromagnetic material such as iron which holds the yoke 35 and which is fixed to the leaf springs 42 and 43. The electromagnetic actuator 18 is configured by providing a pair of shield plates 44 and 45.

Here, the leaf springs 42 and 43 respectively have support holes 42a and 43a for supporting the moving portion 41 in the center thereof, and spiral cut portions 42b and 43b around the support holes 42a and 43a. Are formed to elastically hold the moving portion 41.

The control means 3 has, for example, a frequency fm = 10k.
An oscillator 19 for supplying a light source phase modulation signal of Hz, and a driver 20 for supplying a modulation signal to the phase modulator 12.
A photodetector element 21 such as a photodiode for detecting the return light from the laser resonator 2 reflected by the mirror 13 and converting it into a detected reflected light signal; a light source phase modulation signal from the oscillator 19; A synchronous detection circuit 22 for inputting the detected reflected light signal and generating a resonator length error signal and a reflected light signal corresponding to the deviation (error) of the resonator length with respect to the laser light incident on the laser resonator 2; Detection circuit 2
The servo circuit 23 controls the electromagnetic actuator 18 based on the resonator length error signal and the reflected light signal from the servo circuit 23 to perform resonator length servo.

Next, the laser resonator 2 by the control means 3
The principle of detecting the resonator length error signal in 1 will be described. The laser resonator 2 resonates when the optical path phase difference Δ is an integral multiple of 2π, and the reflection phase largely changes near the resonance phase. The frequency of the laser resonator 2 is controlled by utilizing this phase change.

Generally, when a nonlinear optical crystal element having a refractive index n and a thickness L is present inside the Fabry-Perot resonator, the optical path phase difference Δ is 4πnL / λ. If the single-pass transmittance is T, the single-pass SHG conversion efficiency is η, the incident surface reflectance is R ₁ , and the exit surface reflectance is R ₂ , then the complex reflectance r is

[0035]

[Equation 1]

It becomes

Here, R _m = R ₂ (T (1-η)) ² . The absolute value of r (power reflectance) at this time is shown in FIG.
7 shows the phase (reflection phase), respectively. Utilizing this phase change, the resonance frequency f ₀ of the laser resonator 2 and the frequency f _C of the incident laser light from the laser light source 11 are matched (in an integral multiple relationship).

The incident laser light of frequency f _C (for example, 500 to 600 THz) from the laser light source 11 is subjected to phase modulation of frequency f _m (for example, 10 MHz) by the phase modulator 12, and side band f _C + f _m. Is set up. With respect to the return light from the laser resonator 2 having the resonance frequency f ₀ , the resonator length error signal having the polarity can be obtained by detecting the beats having the frequencies f _C and f _C + f _m .

That is, assuming that the electric field E of the incident laser light from the laser light source 11 is E ₀ exp (iω _c t), the electric field after modulation is E ₀ exp (i (ω _c t + β sin (ω _m
t)). Here, ω _c is the angular frequency of the incident laser light having the fundamental wavelength, ω _m is the angular frequency of the modulation signal of the phase modulator 12, and β is the modulation index. If this modulation index β is sufficiently small, for example β <0.2, then ω _c and 2
It is only necessary to consider the two sidebands ω _c ± ω _m . Therefore, the electric field E of the incident laser light is

[0040]

[Equation 2]

It becomes as follows. Where J ₀ (β), J
₁ (β) is a Bessel function of 0th order and 1st order, respectively.

Next, in the electric field of the reflected light from the laser resonator 2, each term has a complex reflectance with respect to ω _c and two side bands ω _c ± ω _m ,

[0043]

(Equation 3)

It becomes as follows.

However,

[0046]

(Equation 4)

[0047] In this case, a _{β <0.2, J 0 (β} ) ~ (1-β 2/2) become a _{^{1/2 J 1 (β) ~β /}} 2,

[0048]

(Equation 5)

Is as follows.

Therefore, the reflected light intensity | E | ² is
Ignoring the second and higher terms of β,

[0051]

(Equation 6)

Sin (ω _m t), cos (ω _m
It is represented by the equation of t).

However,

[0054]

(Equation 7)

[0055]

(Equation 8)

When such reflected light is synchronously detected by applying an appropriate phase to the original modulation signal (angular frequency ω _m ), sin
(Ω _m t) and cos (ω _m t) are equations (Equation 7),
(Equation 8) is obtained. Of these, sin (ω _m t)
The resonator length error signal can be obtained from (Equation 8), which is the coefficient of

The states of the reflected light intensity | E | ² and the cavity length error signal are shown in FIGS. 8 and 9, respectively. Here, when the laser resonator 2 is in a resonance state with respect to the incident laser light, the energy of the reflected light intensity is sufficiently absorbed by the laser resonator 2, so that the return light shows a minimal property.

Next, the function of the laser light generator will be described.

First, as shown in FIG. 1, the green laser light having a wavelength of 532 nm emitted from the laser light source 11 passes through the phase modulator 12 and the semi-transmissive mirror 13 to be the laser resonator 2 as an incident laser light. Incident on.

The incident laser light incident on the laser resonator 2 passes through the non-linear optical crystal element 17 and is reflected by the reflecting mirror 15 as a laser light having a wavelength of 266 nm, reflected by the mirror 13 and input to the photo-detecting element 21.

Then, the detection reflected light signal generated by the photo-detecting element 21 based on the incident laser light is output from the terminal t1.
The light source phase modulation signal from the oscillator 19 is input to the synchronous detection circuit 22 from the terminal t2, and the synchronous detection circuit 22 concerned
At, the resonator length error signal and the reflected light signal are generated.

FIG. 10 shows how each signal is generated in the synchronous detection circuit 22 at this time.

First, as shown in FIG. 11, the detected reflected light signal input from the terminal t1 is added with a modulation signal of, for example, a frequency of 10 kHz by the phase modulator 12, and the detected reflected light signal is a low pass filter (LPF). ) 51 to remove the modulated signal and add an offset to generate a reflected light signal. At this time, as shown in FIG.
In the intensity of the reflected light signal shown in, the amount of reflected light indicated by the broken line, that is, the bright level is set to 0 level.

On the other hand, the detected reflected light signal input from the terminal t1 is introduced into the bandpass filter (BPF) 52 and the modulated signal shown in FIG. 12 is taken out. This modulated signal is
The sin (ω _m t) component shown in FIG. 13 and co shown in FIG.
It is separated into the s (ω _m t) component, and its envelope is taken out as a resonator length error signal. In this case, since the sin (ω _m t) component is excellent in its envelope shape, the term of this sin (ω _m t) is extracted as the resonator length error signal.

That is, the modulation signal obtained by the bandpass filter 52 is input to the sample-and-hold circuit 53 in order to obtain the term of sin (ω _m t).

Further, a light source phase modulation signal having a frequency fm = 10 kHz as shown by A in FIG. 15 is inputted from the terminal t2, and this light source phase modulation signal is inputted to the clock generating circuit 54 and binarized. At 15, the clock signal shown at B is generated.

Subsequently, this clock signal is input to the phase delay circuit 55 and is subjected to a predetermined amount of phase delay as shown by C in FIG. 15 to obtain a sampling clock signal.

Next, this sampling clock signal is input to the sample and hold circuit 53, the modulation signal shown in FIG. 12 is sampled and held, and the synchronous detection output as shown by D in FIG. 15 is obtained. can get.

Then, this synchronous detection output passes through the low pass filter (LPF) 56 and the sin shown in FIG.
The resonator length error signal shown in FIG. 9 corresponding to the envelope of the (ω _m t) component is obtained.

The resonator length error signal and the reflected light signal obtained as described above are input to the servo circuit 23, and the electromagnetic actuator 18 is controlled based on each of these signals, and the resonator length of the laser resonator 2 is controlled. Servo is performed.

Specifically, FIG. 16 shows a state in which the resonator length servo is performed in the servo circuit 23, and FIG. 17 shows a timing chart of control of opening / closing of the servo loop in this case. In FIG. 17, a and b are the cavity length error signal and the reflected light signal, respectively, and c to h are c in FIG.
Each signal at the positions of ~ h is shown.

In this servo loop, pull-in is performed when the reflected light signal is above a predetermined level and when the resonator length error signal a crosses the zero level. Also, the resonator length error signal a and the reflected light signal b
Shows the case where side mode signals a ₂ and b ₂ occur in addition to the basic mode signals a ₁ and b ₁ . As described above, the incident laser beam may sometimes have side modes such as a transverse mode and a longitudinal mode in addition to the fundamental mode due to various conditions. Need to avoid.

As shown in FIG. 16, the reflected light signal b is offset by the offset section 62 so that the baseline becomes zero level. In this case, in the reflected light signal b, the side where the laser resonator 2 is in the resonance state and the reflected light (return light) from the laser resonator 2 is small, that is, the dark side in FIG. 8 is positive.

The resonator length error signal a and the reflected light signal b are
Both are compared by a comparator 63, 64 with a required slice level, that is, with a slice level higher than the level of each side mode a ₂ , b ₂ signal and lower than the level of the basic mode signals a ₁ , b ₁ . As a result, the side mode a ₂ and b ₂ signals and various noises are removed, and signals c and e having a level higher than the slice level for only the basic mode signals a ₁ and b ₁ are obtained.

The signal c obtained in the comparator 63
Is input to the monostable multivibrator 65, and the gate d is opened for an appropriate time τ from the rise of the signal c.

Then, in the OR circuit 66, a signal f which turns on when either the signal d or the signal e is turned on is obtained.

On the other hand, the resonator length error signal a is input to the comparator 67 and is compared at zero level, and the fundamental mode signal a ₁ and the side mode signal a _{2 of} the resonator length error signal a cross the zero level. Sometimes a signal g indicating a signal change is obtained.

Further, the signal g is input to the D type flip-flop circuit 68 as a clock. In this case, when the signal f from the OR circuit 66 is "1" and the signal g rises, the signal h rises, the switch 60 is turned on, and the servo pull-in is started. Here, in the flip-flop circuit 68, the OR circuit 6
The ON state is held until the signal f from 6 becomes "0".

Then, the resonator length error signal a is input to the phase compensation circuit 69 for phase compensation, and then to the driver 70 via the switch 60 in the ON state, and the electromagnetic actuator 18 It will be driven as shown.

First, the phase-compensated resonator length error signal a
A drive current (servo current) is supplied from the driver 70 to the coil 32 of the electromagnetic actuator 18 in response to the above.

At this time, since the direction of the servo current flowing through the coil 32 and the direction of the magnetic field generated by the permanent magnet 34 are substantially orthogonal to each other, a thrust force is applied to the moving portion 41 in the vertical direction in FIG. Be moved.
Here, the reflecting mirror 15 is fitted and fixed to the moving unit 41, and the moving of the reflecting mirror 15 together with the moving unit 41 in the optical axis direction is controlled.

In this case, when the resonator length of the laser resonator 2 is selected to resonate with the incident laser light, the amount of light reflected from the laser resonator 2 becomes small and the photodetector element 21
The intensity of the detected reflected light signal from is small. At this time, when the resonator length error signal value becomes zero, the electromagnetic actuator 18
Is stopped at this position and held in resonance.

In the laser resonator 2, the magnetic circuit is a closed magnetic circuit because the magnetic circuit is a closed magnetic circuit even though no conductor or magnetic material typified by metal is arranged inside the coil 32 of the electromagnetic actuator 18. A large thrust is obtained by the induction action.

At this time, since the cylindrical plate 33 made of a metal material having a low electric resistance value is provided between the coil 32 and the permanent magnet 34, the surface of the coil 32 and the permanent magnet 3 are provided.
The generation of eddy currents on the surface of No. 4 is suppressed, and it becomes possible to realize a transfer characteristic with less phase rotation.

By mounting the laser resonator 2 on a laser light generator having a laser light source, it becomes possible to stably and surely emit laser light having a desired resonance frequency.

Here, one experimental example will be described.
This experiment is based on a comparison between the laser resonator 2 shown in the present embodiment and a laser resonator in which the cylindrical plate 33 is not arranged in the moving portion 41 of the electromagnetic actuator 18 that is a component thereof. The impedance characteristics of the are investigated. Hereinafter, the electromagnetic actuator 18 shown in the present embodiment will be referred to as sample 1, and the electromagnetic actuator of the comparative example will be referred to as sample 2.

Here, as the impedance characteristic, the dependence of the electric resistance value (Ω) and the phase (°) on the change of frequency was measured.

Regarding the experimental results, FIG. 18 shows the electric resistance value change in the case of sample 1, FIG. 19 shows the phase change, and FIG. 20 and FIG. 21 show the case of sample 2 similarly. As described above, it can be seen that in the sample 1, the phase around is clearly reduced in the vicinity of 100 kHz as compared with the sample 2.

Therefore,

[0090]

According to the laser resonator and the laser light generator using the same of the present invention, the resonator length of the laser resonator can be stably and surely maintained in a wide servo band of several tens of kHz with a small frequency characteristic around the phase. It becomes possible to control.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing a laser light generator according to the present embodiment.

FIG. 2 is a perspective view schematically showing an electromagnetic actuator, which is a component of a laser resonator, in an exploded manner and a reflecting mirror fitted and fixed to the electromagnetic actuator.

FIG. 3 is a perspective view schematically showing an electromagnetic actuator and a reflecting mirror.

FIG. 4 is a perspective view schematically showing a partially cutaway electromagnetic actuator having a reflecting mirror fitted and fixed thereto.

FIG. 5 is a perspective view schematically showing an electromagnetic actuator to which a reflecting mirror is fitted and fixed by partially cutting away the cylindrical plate, leaving a cylindrical plate.

FIG. 6 is a characteristic diagram showing absolute values of complex reflectances in a Fabry-Perot resonator.

FIG. 7 is a characteristic diagram showing a reflection phase in a Fabry-Perot resonator.

FIG. 8 is a characteristic diagram showing a reflected light intensity in a Fabry-Perot resonator.

FIG. 9 is a characteristic diagram showing a resonator length error signal based on reflected light in a Fabry-Perot resonator.

FIG. 10 is a block diagram schematically showing a configuration of a synchronous detection circuit.

FIG. 11 is a characteristic diagram showing a detected reflected light signal to which modulated signals are added.

FIG. 12 is a characteristic diagram showing a modulation signal extracted from a detected reflected light signal.

FIG. 13 is a characteristic diagram showing a component of sin (ω _m t) in the modulated signal.

FIG. 14 is a characteristic diagram showing a component of cos (ω _m t) in the modulated signal.

FIG. 15 is a characteristic diagram showing a clock signal generated based on a light source phase modulation signal, a sampling clock signal, and a synchronous detection output.

FIG. 16 is a block diagram schematically showing the configuration of a servo circuit.

FIG. 17 is a characteristic diagram showing a timing chart of control of opening and closing a servo loop in the servo circuit.

FIG. 18 is a characteristic diagram showing the dependence of the electric resistance value on the change in frequency in the electromagnetic actuator according to the present embodiment.

FIG. 19 is a characteristic diagram showing the dependence of phase on a change in frequency in the electromagnetic actuator according to the present embodiment.

FIG. 20 is a characteristic diagram showing the dependence of the electric resistance value on the change in frequency in the electromagnetic actuator of the comparative example of the present embodiment.

FIG. 21 is a characteristic diagram showing the dependence of phase on a change in frequency in the electromagnetic actuator of the comparative example of the present embodiment.

[Explanation of symbols]

 1 Laser Light Emitting Means 2 Laser Resonator 3 Control Means 15, 16 Pair of Reflecting Mirrors 17 Nonlinear Optical Crystal Element 18 Electromagnetic Actuator 31 Coil Bobbin 32 Coil 33 Cylindrical Plate 34 Permanent Magnet 35 Yoke 41 Moving Part 42, 43 Leaf Spring 44, 45 A pair of shield plates

Claims (4)

[Claims] 1. A laser having at least a pair of reflecting means and a nonlinear optical crystal element disposed between the reflecting means, the wavelength of which is converted by resonantly operating the laser light incident on the nonlinear optical crystal element. A laser resonator for generating light, wherein at least one of the reflecting means is fitted and fixed in a cylindrical coil bobbin formed by winding a coil around an outer peripheral portion, and is made of a metal material having a low electric resistance value. A laser characterized by being arranged in an annular yoke made of a ferromagnetic material via a cylindrical plate, and the reflecting means being moved by electromagnetic induction by supplying a drive current to the coil. Resonator. 2. The laser resonator according to claim 1, wherein the metal material having a low electric resistance value, which is a material of the cylindrical plate, is copper or gold. 3. A laser light source for emitting a laser beam of a fundamental wavelength, and at least a pair of reflecting means, and a nonlinear optical crystal element is arranged between the reflecting means, and the laser light source enters the nonlinear optical crystal element. A laser resonator for generating a wavelength-converted laser beam by resonating the generated laser beam, and at least one of the reflecting means is fitted in a cylindrical coil bobbin formed by winding a coil around the outer periphery. It is fixed and placed in an annular yoke made of a ferromagnetic material through a cylindrical plate made of a metal material having a low electric resistance value. A laser beam generator in which the reflection means is moved. 4. The laser beam generator according to claim 3, wherein the metal material having a low electric resistance value, which is a material of the cylindrical plate, is copper or gold.