JPH01157583A - Variable wavelength laser device - Google Patents

Abstract

PURPOSE:To selectively output a laser beam of any wavelength within wide band with ease without enlarging the device by providing a polarization selector unit by which a laser beam having a arbitrary polarization is selected among laser beams emitted from an optical parametric oscillator. CONSTITUTION:When a signal for obtaining a desired wavelength lambda30 is inputted into an input terminal 15, a processor part 17 in a first rotational angle control circuit 14 reads corresponding data from a storage 18 and performs a predetermined operation. A rotary table 11 is rotated to set a phase matching angle theta0 between the optical axis 12 of a nonlinear optical crystal 5 and the optical axis 13 of an incident laser beam 1 at a predetermined value. For this, a desired wavelength lambda laser beam is included in a plurality of emanating laser beams 7 having different polarizations. In contrast, a processor part 23 of a second rotational angle control circuit 22 reads corresponding data from a storage 24 and performs a predetermined operation. Hereby, a rotational angle theta1 of a Gran-Tailor prism 21 is controlled at a predetermined value to assure the output laser beam 30 having the desired wavelength lambda.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention changes the wavelength of the emitted laser light by changing the incident angle of the laser light that enters the nonlinear optical crystal, and changes the wavelength of the emitted laser light. This invention relates to a wavelength tunable laser device that selects and outputs arbitrary laser beams from a plurality of laser beams with different wavelengths, and easily selects a laser beam with a wide band of wavelengths without increasing the size of the device. This relates to a device that allows the user to exit the vehicle.

[Prior Art] Conventionally, as shown in FIG. 5, a wavelength tunable laser device for rice seeds uses an incident laser beam (for example, excitation light of λ: 355 nm).
Collimating lens (2) to increase the power density of (1), entrance mirror (3), and exit mirror (4)
and a rotatable nonlinear optical crystal (5) provided between these mirrors (3) and (4) form an optical parametric oscillator (6), and this optical parametric oscillator (
A prism, an interference filter, or a mirror is provided on the side of the emitted laser beam (7) of 6), and a plurality of laser beams with different wavelengths (for example, λ = 500n) included in the emitted laser beam (7) are provided.
An arbitrary laser beam (for example, ordinary light with λ=500 nm) is selected from among the ordinary light with λ=1230 nm and the extraordinary light with λ=1230 nm) and outputted.

[Problems to be solved by the invention] However, the output laser beam (
In the conventional example of selecting and outputting a laser beam of an arbitrary wavelength from among multiple laser beams of different wavelengths included in 7), the optical path length on the output side of the prism must be lengthened, so the device There was a problem with increasing the size. Moreover, since the emission direction of the laser beam separated by the prism differs depending on the wavelength, the emission direction of the selected laser beam differs each time the wavelength is changed, which poses the problem of complicating position adjustment when used for measurements etc. there were.

In addition, the output laser beam (7
In the conventional example of selecting a laser beam with an arbitrary wavelength from ), the wavelength band that can be selected by one interference filter or mirror is narrow, so it is not possible to select and output a laser beam with a wide band of wavelengths. There is a problem in that a plurality of interference filters and mirrors with different bands must be prepared and replaced for each selected wavelength band.

The present invention was made in view of the above-mentioned problems, and an object of the present invention is to provide a wavelength tunable laser device that can easily select and output laser light with a wide band of wavelengths without increasing the size of the device. This is the purpose.

[Means for Solving the Problems] The present invention provides an optical parametric oscillator that changes the wavelength of a plurality of delivered laser beams with different polarization directions by changing the incident angle of the laser beam incident on a nonlinear optical crystal, and It is characterized by comprising a polarization direction selection device that selects and outputs a laser beam with an arbitrary polarization direction from among a plurality of laser beams emitted from an oscillator.

[Function] Changing the incident angle of the laser beam that enters the nonlinear optical crystal of the optical parametric oscillator changes the wavelengths of the plurality of laser beams with different polarization directions that are emitted from the nonlinear optical crystal. For this reason, the incident angle of the laser beam entering the nonlinear optical crystal is controlled so that the laser beam of the wavelength to be selected and output is included in the output laser beam of the optical parametric oscillator.
When a polarization direction corresponding to a laser beam of a wavelength to be selected and output is selected by the polarization direction selection device, a laser beam of a predetermined wavelength is selected and output.

[Embodiment] FIGS. 1, 2, and 3 show an embodiment of the present invention, and the same parts as in FIG. 5 are given the same reference numerals. Figure 1,
In FIGS. 2 and 3, (6) is an optical parametric oscillator, and (20) is a polarization direction selection device. The optical parametric oscillator (6) includes a nonlinear optical crystal (for example, a urea crystal) (5), an entrance mirror (3) and an exit mirror (4) disposed on the entrance and exit sides of the nonlinear optical crystal (5).
) (not shown in Figure 1) and this incident mirror (3)
A collimating lens (2) (not shown in FIG. 1) provided at the front stage of the rotary table (11) for rotating the nonlinear optical crystal (5) in the direction of the arrow; ) by rotating the nonlinear optical crystal (5).
optical axis (12) and the incident laser beam (for example, the wavelength is 355
nm excitation light) (1) and the optical axis (13) (t
Phase matching angle) θ that satisfies the phase matching condition of ype-2.

A first rotation angle control circuit (14) that controls the wavelength λ of a plurality of emitted laser beams (7) having different polarization directions (for example, the wavelength λS of ordinary light and the wavelength λj of extraordinary light shown in FIG. 4) by changing the It consists of

This first rotation angle control circuit (14) is connected to a CPU (central processing unit) (
16), a memory (18) connected to a calculation section (17) of the CPU (16), and a motor driver (19) connected to the output side of the calculation section (17).

The polarization direction selection device (20) includes a grand tiller prism (21) as an optical component having polarization direction selection ability provided on the output laser beam (7) side of the optical parametric oscillator (6), Prism (21
) rotates around the optical axis (13) of the emitted laser beam (7).
It consists of Said second rotation angle control circuit (22)
includes the CPU (16) coupled to the wavelength control signal input terminal (15), a memory (24) coupled to the arithmetic unit (23) of this CPU (16), and the arithmetic unit (23). ) coupled to the output side of the motor driver (25
).

Specifically, the grand tiller prism (21) is 1
．． As shown in Figures 2 and 3, the exit mirror (4)
A shaft (27) mounted on the support body (26) opposite to the exit mirror (4) and rotated by the motor driver (25) rotates around its central axis (28) as shown in FIG. When it rotates in the direction of the arrow (or the opposite direction), it rotates around the optical axis of the output laser beam (30) in the direction of the arrow in the figure (or the opposite direction).

In the above configuration, when a signal for obtaining a target wavelength λ (for example, ordinary light of λ=500 nm) (30) is input to the input terminal (15), that signal is input to the CPU (16).
) are added to the calculation units (17) and (23). Then,
The calculation unit (17) of the first rotation angle control circuit (14) reads the corresponding data from the memory (18), performs a predetermined calculation, and sets the motor driver (19) to the desired rotation angle (θ).

), the rotary table (11) is rotated to adjust the phase matching angle θ between the optical axis (12) of the nonlinear optical crystal (5) and the optical axis (13) of the incident laser beam (1). is controlled to a predetermined value (for example, θ=90 degrees). For this reason,
Among the plurality of emitted laser beams (7) with different polarization directions,
A laser beam with a target wavelength λ (for example, ordinary light with λ=500 nm) is included (extraordinary light with λ=123 onm also exists).

On the other hand, the calculation section (23) of the second rotation angle control circuit (22)
reads the corresponding data from the memory (24), performs a predetermined calculation, sends a signal corresponding to the desired rotation angle (θ1) to the motor driver (25), and adjusts the rotation angle of the grand tiller prism (21). θ1 is controlled to a predetermined value (for example, the state shown in FIGS. 1 and 3 when θ1=0 degrees), and the output laser beam (30) with the target wavelength λ (for example, λ=5oonm) is controlled.
(normal light) is obtained. Also, the desired output laser beam (
30) is an extraordinary light of λ=1230 nm, θ.

= 90 degrees, and θ1 = 90 degrees. Furthermore, θ. When is controlled to 9 degrees and θ is controlled to a value between 0 and 90 degrees, the power ratio of the ordinary light of λ = 500 nm and the extraordinary light of λ = 123 onm becomes a value corresponding to the rotation angle θ1. An output laser beam (30) is obtained. Therefore, θ. to a constant value (
For example, by fixing the angle θ□ to 90 degrees and changing θ□ within the range of 0 to 90 degrees, the power ratio between the ordinary light and the extraordinary light contained in the output laser beam (3o) can be changed.

[Effects of the Invention] As described above, the wavelength tunable laser device according to the present invention uses the polarization direction selection device to select a laser beam with an arbitrary polarization direction from among a plurality of output laser beams with different polarization directions output from the optical parametric oscillator. Since the system selects and outputs wavelengths, it is possible to make the device more compact compared to the conventional method that selects wavelengths using prism spectroscopy, and it also allows for easier selection of broadband wavelengths compared to the conventional method that selects wavelengths using interference filters or mirrors. Laser light can be selected and output.

Further, when the polarization direction selection device is formed of an optical component having polarization direction selection ability and a rotation angle control circuit that controls the rotation angle of the optical component using a signal corresponding to a wavelength to be selected and output. Since the wavelength can be selected using a CPU or the like, remote control is possible and operational safety can be ensured.

[Brief explanation of the drawing]

1 to 3 show an embodiment of the wavelength tunable laser device according to the present invention, FIG. 1 is an explanatory diagram explaining the configuration of the device, FIG. 2 is a front view showing the external appearance of the device, Fig. 3 is an enlarged perspective view showing a part of Fig. 2, and Fig. 4 is a general diagram showing the relationship between the phase matching angle and the wavelength of the emitted laser beam that satisfies the phase matching condition of type-2 of the optical parametric oscillator. The characteristic diagram, FIG. 5, is an explanatory diagram showing a conventional example. (1)...Incoming laser beam, (5)...Nonlinear optical crystal, (6)...Optical parametric oscillator, (7)...
- Output laser beam, (20)...Polarization direction selection device, (
21)...Gruntiller prism (an example of an optical component having the ability to select polarization direction), (30)...Output laser light. Applicant Hamamatsu Photonics Co., Ltd.

Claims (2)

[Claims] (1) An optical parametric oscillator that changes the wavelength of a plurality of emitted laser beams with different polarization directions by changing the incident angle of the laser beam incident on a nonlinear optical crystal; A wavelength tunable laser device comprising a polarization direction selection device that selects and outputs laser light in a polarization direction. (2) The polarization direction selection device includes an optical component that is provided on the output laser beam side of the optical parametric oscillator and has the ability to select the polarization direction. 2. The wavelength tunable laser device according to claim 1, further comprising a rotation angle control circuit for controlling a rotation angle control circuit.