JPH08316559A - Laser wavelength stabilizing device - Google Patents

Abstract

PURPOSE: To make the wavelength of an outputted laser beam coincident with a reference wavelength by a method wherein an isolated laser beam of axial mode is received by a wavelength reference device, the laser beam transmitted through the reference device is converted into electrical signals through a photoelectric converter to operate a wavelength controller. CONSTITUTION: When an He-Ne laser of resonant wavelength L is used as a laser ray source 1, a laser ray source possessed of an axial mode represented by a formula, fi=C/2L, can be obtained, where c denotes the velocity of light. The laser beams of these two axial modes emitted from the laser ray source 1 are capable of being separated into two laser beams of different axial modes through a mode separating optical system 2. Therefore, a laser beam of axial mode a separated by the mode separating optical system 2 is inputted into a wavelength reference device 3. The laser beam transmitted through the wavelength reference device 3 is converted into electrical signals through a photoelectric converter 4, and the converted electrical signals are inputted into a wavelength controller 5. The wavelength of a laser beam of axial mode a can be set coincident with the center wavelength of the wavelength reference device 3 by controlling the laser ray source 1 using the electrical signals outputted from the photoelectric converter 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser wavelength stabilizing device for stabilizing the oscillation wavelength of a laser.

[0002]

2. Description of the Related Art A conventional laser wavelength stabilizer of this type is a Fabry-Perot interferometer.
(ter) resonance spectrum or the center of the absorption spectrum of atoms or molecules is used as the wavelength reference, and the wavelength of the laser light obtained from the single-axis mode laser light source is controlled to match this wavelength reference. The center of the absorption spectrum is detected by frequency-modulating the laser light and performing resonance on the signal light obtained by the resonance or absorption spectrum of the laser light, which is the frequency reference, by phase-sensitive detection with a frequency-modulated signal. Alternatively, the differential waveform of the absorption characteristic is used.

[0003]

Since the conventional laser wavelength stabilizing device as described above detects the center of the resonance spectrum or the absorption spectrum by frequency-modulating the laser light as described above, the laser to be stabilized is desired. The wavelength itself is frequency-modulated, limiting its usefulness. Further, since the laser light is branched into two and a part of the laser light is used for detecting the frequency reference signal and the rest is output to the outside as a stabilizing light source, the light intensity of the laser light source to be output becomes weak. There were problems such as. In particular, when the absorption spectrum that is the frequency reference is weak, it is necessary to increase the ratio of the laser light branched for frequency reference detection in order to increase the stability. The laser light emitted becomes even weaker.

[0004]

A laser wavelength stabilizing device according to the present invention uses a laser light source for emitting a plurality of axial mode light beams having different wavelengths as a laser light source, and the light beam emitted from the laser light source. Is separated into two light beams having different axial modes using a separation optical system, one of the separated light beams of the axial mode (a) is received by a wavelength reference device and converted into an electric signal by an electric converter. A means for operating the wavelength controller to match the wavelength of the optical beam of the axial mode (a) with the reference wavelength of the wavelength reference device, and outputting the other separated optical beam of the axial mode (b) as the stabilizing light source. It is characterized in that it is provided with a means for doing.

Further, a laser light source which emits a plurality of axial mode light beams having different wavelengths is used as a laser light source, and a light beam emitted from the laser light source is separated into two light beams having different axial modes by using a separation optical system. A means for separating the beam into two beams, one of the separated optical beams of the axial mode (a) is received by the wavelength reference device and converted into an electric signal to operate the wavelength controller, and the wavelength of the optical beam of the axial mode (a) is converted into the wavelength. Means for matching the reference wavelength of the reference device, means for outputting the other separated light beam of the axial mode (b) as a stabilizing light source, part of the optical beam of the axial mode (a) and axial mode (b) And a means for correcting the frequency of the light beam of the axial mode (b) so that the beat frequencies of these light beams coincide with the reference frequency.

[0006]

Controlling the beat frequency to match the reference frequency is easier than controlling the laser wavelength to match the reference wavelength, and the stability of the wavelength of the light beam in the axial mode (b) is controlled. It is easy to keep the stability of the wavelength of the light beam in the mode (a) at the same level. Further, the difference in wavelength between these two axial modes can be accurately obtained from the beat frequency. When the axial mode (b) light beam is extracted to the outside and used, it is independent of the axial mode (a) light beam used to obtain the wavelength reference signal, and therefore the stabilization to be used. The generated laser light is not subjected to frequency modulation, and there is no restriction that only part of it can be used.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the configuration of the wavelength stabilization device of the present invention, in which 1 is a laser light source. The laser light source 1 of this embodiment has a plurality of axis modes.
A laser light source that oscillates in (axial mode) is used. If, for example, a He-Ne laser having a resonance wavelength of L is used as the laser light source 1, C is the speed of light and the axial mode interval of fi = C / 2L.
A laser light source having two axial modes oscillating in (cavity modes pacing) can be obtained. For a He-Ne laser, the beat frequency fi between these two axial modes is 600M.
The frequency is generally from Hz to 1.2 GHz. Further, since the polarization planes of these two axial modes are orthogonal to each other, it is possible to easily separate the light beams for each single axial mode using the mode separation optical system 2 such as a polarization beam splitter.

Therefore, the light beam of one axial mode (a) separated by the mode separation optical system 2 is input to the wavelength reference device 3, the transmitted light is converted into an electric signal by the photoelectric converter 4, and the wavelength is controlled. The wavelength controller 5 uses the electric signal from the photoelectric converter 4 to input the wavelength of the light beam of the axial mode (a) to the laser source so that the wavelength of the light beam coincides with the center wavelength of the wavelength reference unit 3. Control 1 As the wavelength reference device 3, a Fabry-Perot interferometer or a wavelength reference device using an absorption spectrum of atoms or molecules existing in the oscillation wavelength range of the laser light source 1 can be used as in the conventional device. The control is similar to that of the conventional device. On the other hand, the light beam emitted from the laser light source 1 stabilized by the above control is separated by the mode separation optical system 2 as described above, and is different from the axial mode (a) used for the stabilization control. The light beam in the axis mode (b) is output as a stabilized light source to the outside.

It is known that the intensity of each axial mode light beam that oscillates in a plurality of axial modes is about the same as the intensity of a laser of the same type that oscillates in a single axial mode.
Therefore, the optical beam of the axial mode (b) output to the outside is
It is possible to obtain a light source which is not frequency-modulated as in the conventional device and has sufficient intensity. However, while the laser light source 1 is in operation, the above-mentioned resonance wavelength L is always slightly changed due to the influence of temperature and the like. Therefore, it is necessary to correct this change in the resonance wavelength L.

That is, a part of the optical beam of the axial mode (b) is taken out by the beam splitter 7, and a part of the optical beam of the axial mode (a) is made to interfere with the beam splitter 9 by the beam splitter 8. Converter 1
0 is input to detect the beat frequency fi + fΔ (fΔ is the frequency shift amount due to the change of the resonance wavelength L). In addition, the wave plate 11 includes a light beam in the axial mode (a) and an axial mode (b).
It is used to match the plane of polarization with the light beam of. The output of the photoelectric converter 10 is input to the shift frequency controller 12, and the shift frequency controller 12 outputs the beat frequency f.
i + fΔ is compared with the reference frequency fr13, and the difference is output to the optical frequency shifter 6, and the optical frequency shifter 6 corrects the frequency shift amount fΔ of the optical beam in the axial mode (b). The frequency shifter 6 can be easily realized by an acousto-optic device that uses Bragg diffraction or a rotating disk that uses the Doppler effect.

As described above, the laser wavelength stabilizer of this embodiment uses a laser light source that oscillates in a plurality of axial modes having different wavelengths, and one of the two axial modes (a) is selected. The light beam is used for stabilizing the wavelength of the laser light source, and the other axial mode (b) is output as a stabilized light source, and the frequency shift amount f with the change of the resonance wavelength L is f.
For the correction of Δ, a part of the light beam in the axial mode (a) and a part of the light beam in the axial mode (b) are taken out and the beat frequency thereof is corrected at a predetermined reference frequency fr13.
As is well known, the beat frequency can be detected with high sensitivity, and the amount of light required for this correction is small, so that a stabilized light source with no modulation and high output can be obtained. It is also possible to use a device that outputs a stabilized light source in which the reference frequency 13 is varied and predetermined modulation is performed.

[0012]

As described above, the laser wavelength stabilizing device of the present invention has an effect that a stabilized light source with no modulation and high output can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

[Explanation of symbols]

 1 Laser Light Source 2 Mode Separation Optical System 3 Wavelength Reference Device 4 Photoelectric Converter 5 Wavelength Controller 6 Frequency Shifter 7-9 Beam Splitter 10 Photoelectric Converter 11 Wave Plate 12 Shift Frequency Controller 13 Reference Frequency

Claims (2)

[Claims] 1. A light beam from a laser light source is received by a wavelength reference device, converted into an electric signal to operate a wavelength controller, and the wavelength of the light beam from the laser light source coincides with the reference wavelength of the wavelength reference device. In the laser wavelength stabilization device for controlling the laser light source to obtain a stabilized light source, a laser light source that emits a plurality of axial mode light beams having different wavelengths is used as the laser light source, and the light beam emitted from the laser light source is separated and separated. Means for separating into two light beams of different axial modes using a system, one of the separated light beams of the axial mode (a) is received by the wavelength reference device and converted into an electric signal by an electric converter, and the wavelength A means for operating the controller to match the wavelength of the light beam of the axial mode (a) with the reference wavelength of the wavelength reference device, and the other separated light beam of the axial mode (b) as the stabilizing light source. A laser wavelength stabilizing device comprising: a means for outputting. 2. A light beam from a laser light source is received by a wavelength reference device, converted into an electric signal, and a wavelength controller is operated to match the wavelength of the light beam from the laser light source with the reference wavelength of the wavelength reference device. In the laser wavelength stabilization device for controlling the laser light source to obtain a stabilized light source, a laser light source that emits a plurality of axial mode light beams having different wavelengths is used as the laser light source, and the light beam emitted from the laser light source is separated and separated. Means for separating into two light beams of different axial modes using a system, one of the separated light beams of the axial mode (a) is received by the wavelength reference device and converted into an electric signal to operate the wavelength controller Means for matching the wavelength of the light beam of the axial mode (a) with the reference wavelength of the wavelength reference device, and a means for outputting the other separated light beam of the axial mode (b) as the stabilizing light source. A part of the light beam of the axial mode (a) and a part of the light beam of the axial mode (b) are taken out, and the axial mode (b) is adjusted so that their beat frequencies coincide with the reference frequency.
A laser wavelength stabilizing device comprising means for correcting the frequency of the light beam.