JPH0514867U - Optical wavelength meter - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] To realize a compact, inexpensive, long-life device capable of highly accurate wavelength measurement. [Composition] The absorption line of gas is used as a frequency reference
A frequency-stabilized laser light source 3 that emits a reference light by controlling the oscillation frequency of the diode so that it is always constant by an injection current or a temperature, and an optical system 4 for introducing a measurement light. A Michelson interferometer 1 having a movable mirror 14 in its optical system, a photodetector 2 for detecting an interference signal between the reference light and the light to be measured, and a reference light from the frequency stabilizing laser light source 3. And the measuring light incident optical system 4
The wavelength of the light to be measured is measured by simultaneously injecting the light to be measured from the above into the Michelson interferometer 1 and measuring the intensity change of the interference caused by displacing the movable mirror 14 with the photodetector 2. The feature is that they are asked.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an optical wavelength meter for measuring the wavelength of light, and more particularly to an optical wavelength meter that is compact, inexpensive, has a long life, and has higher measurement accuracy.

[0002]

[Prior Art]

An optical wavelength meter is a device that measures the wavelength of a light source used for optical communication, optical application equipment, and various optical measurements. Currently, as a method for measuring the wavelength of light, an optical spectrum analyzer is used to measure the optical power corresponding to each wavelength by spectroscopy, and a spectroscope that determines the peak wavelength or center wavelength from the spectrum is used. , An optical wave plate such as an interference film filter type that uses the ratio of reflection and transmission of an interference film filter to change according to wavelength, and an optical rotator type that uses the polarization plane of a crystal to rotate according to wavelength. And the Michelson interferometer that determines the wavelength by measuring the intensity change of the interference caused by displacing the moving mirror with the Michelson interferometer. Among these, the Michelson interferometer is superior in view of the fact that it is possible to perform high-precision measurement of 10 ⁻⁶ orders or more and is easy to handle.

As shown in FIG. 2, the optical wavelength meter based on the Michelson interferometer uses the Michelson interference composed of the reference light and the light to be measured, which is composed of Hahmira-11, Mira-12 and 13, and the movable mirror 14. The interference signal generated when the movable mirror 14 is displaced at the same time is incident on the meter 1 is photoelectrically converted by the photodetector 2, and the wavelength of the light to be measured is obtained by a calculation unit (not shown).

[0004]

[Problems to be solved by the device]

However, in the optical wavelength meter by the Michelson interferometer shown in the above-mentioned prior art, its measurement resolution (accuracy) is almost the same as the stability (absolute accuracy of wavelength) of the He-Ne laser used for the light source. It has been determined and was about 1 × 10 ⁻⁶ . Further, since the He-Ne laser is a gas laser, it is difficult to miniaturize it and its life is short.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide an optical wavelength meter that can be miniaturized, inexpensive, and have a long life, and that can perform more accurate wavelength measurement. It was done.

[0006]

[Means for Solving the Problems]

 The configuration of the present invention for solving the above-mentioned problem is to use a gas absorption line as a frequency reference and control the oscillation frequency of a laser diode so that it is always constant by the injection current or the temperature. Stabilized laser light source that emits light, a measurement light incidence optical system that inputs the measured light, a Michelson interferometer that has a moving mirror in the optical system, and the interference between the reference light and the measured light. A photodetector for detecting a signal, wherein the reference light from the frequency-stabilized laser light source and the light to be measured from the measurement light incidence optical system are simultaneously incident on the Michelson interferometer, and the movable mirror The wavelength of the light to be measured is obtained by measuring the intensity change of the interference caused by displacing the light with the photodetector.

[0007]

[Action]

 According to the present invention, a frequency-stabilized laser light source whose oscillation frequency is fixed to a gas absorption cell is used as a light source of an optical wavelength meter. Therefore, as compared with a light source using a He-Ne laser, the wavelength accuracy can be improved by two to three digits, and a small-sized, inexpensive, long-life device can be obtained.

[0008]

【Example】

 Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the optical wavelength meter of the present invention, which uses a Michelson interferometer. In FIG. 1, the same elements as those in FIG. 2 are designated by the same reference numerals, and overlapping description will be omitted. In FIG. 1, reference numeral 3 is a frequency stabilizing laser light source for emitting a reference light. The frequency stabilizing laser light source 3 is a laser diode 31 and a harness for taking out an output. It is composed of a humilla-32, a harhumilla-33 for power monitoring, an absorption cell 34 for Rb gas, photodetectors 35 and 36, and a control circuit 37 for controlling the injection current of the laser diode 31. .. The light emitted from the laser diode 31 is branched by the half mirror 33, one of which is incident on the Rb gas absorption cell 34, and the transmission intensity thereof is detected by the photodetector 35. The other one is detected by the photodetector 36 for power monitoring, both signals are output to the control circuit 37, and the oscillation wavelength of the laser diode 31 is controlled to be always constant. Reference numeral 4 is a measuring light incidence optical system for making the measured light incident, and 5 is a mirror for guiding the measured light to the Michelson interferometer 1.

In such a configuration, the reference light emitted from the frequency stabilizing laser light source 3 is controlled so that the oscillation wavelength is always constant, and the reference light emitted through the half mirror 32 and the measuring light incident optical system. The light to be measured emitted from the system 4 and guided by the mirror 5 is simultaneously incident on the Michelson interferometer 1 including the half mirrors 11, mirrors 12, 13 and the movable mirror 14 to displace the movable mirror 14. The interference signal at that time is photoelectrically converted by the photodetector 2, and the wavelength of the light to be measured is obtained by a calculation unit (not shown).

Here, the wavelength of the reference light emitted from the frequency stabilizing laser light source 3 is λ r, the wavelength of the light to be measured emitted from the measurement light incident optical system 4 is λ m, and the air refractive index is na. When the displacement of the moving mirror 14 is L, the interference signal θr due to the reference light and the interference signal θm due to the measured light are respectively expressed by the following equations. θr = (2π / λr) · 4na L ... θm = (2π / λm) · 4na L ... In the above configuration, the reference light and the measured light pass through the same optical path in opposite directions, and the reference light and the measured light Since the air refractive index na and the displacement L of the movable mirror 14 are the same, if the ratio of the above equations is taken, λm = λr · θr / θm ... And the wavelength of the measured light can be obtained from this equation. ..

As a result, the measurement accuracy of the conventional optical wavelength meter is determined by the wavelength accuracy (~ 1 × 10 ^-6 ) of the He-Ne laser used for the light source, but it is the present invention. In addition, by using a frequency-stabilized laser light source with a wavelength accuracy of 1 × 10 ^-8 to 10 ^-9 , it is possible to improve the measurement accuracy of the optical wavelength meter by a few digits. The LD light source is smaller, cheaper, and has a longer life than He-Ne lasers, which is a feature of the optical wavelength meter of the present invention.

In the above embodiment, the gas absorption cell 34 used in the frequency stabilizing laser light source 3 is not limited to Rb, but may be Cs (cesium) or NH4 (acetylene). The interferometer is not limited to the Michelson type, but may be a Fizeau type or a Mach-Zehnder type.

[0013]

[Effect of the device]

 As described above in detail with reference to the embodiments, according to the present invention, it is possible to realize an optical wavelength meter that can be made small in size, inexpensive, and have a long life, and that can measure wavelengths with higher accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an optical wavelength meter of the present invention.

FIG. 2 is a configuration diagram showing the principle of an optical wavelength meter using a Michelson interferometer.

[Explanation of symbols]

 1 Michelson Interferometer 2, 35, 36 Photodetector 3 Frequency Stabilized Laser Light Source 4 Optical System for Incident of Measurement Light 5, 12, 13 Mirror 11, 32, 33 Haar Mirror 14 Moving Mirror 31 Ray The diode 34 Rb gas absorption cell 37 Control circuit

Claims (1)

[Scope of utility model registration request] 1. A frequency stabilization laser which emits a reference light by controlling an oscillation frequency of a laser diode so that it is always constant by an injection current or a temperature by using a gas absorption line as a frequency reference. A light source, a measurement light incident optical system for injecting the measured light, a Michelson interferometer having a movable mirror in the optical system, and a photodetector for detecting an interference signal between the reference light and the measured light. The reference light from the frequency-stabilized laser light source and the measured light from the measurement light incidence optical system are simultaneously incident on the Michelson interferometer, and the interference caused by displacing the movable mirror. An optical wavelength meter, wherein the wavelength of the light to be measured is obtained by measuring the intensity change with the photodetector.