JP2998399B2 - Frequency stabilized light source - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency-stabilized light source that stabilizes the frequency of a laser, and more particularly to a frequency-stabilized light source that does not require setting change of a drive circuit, a frequency discriminator, and the like for each laser.

[0002]

2. Description of the Related Art FIG. 4 shows the configuration of a conventional embodiment. In FIG. 4, 1 is a semiconductor laser, 2 is a lens, 3 is an optical isolator, 4 is an optical branching component as a branching unit, 5 is an absorption cell as a frequency discriminating element, 6 is a photodetector, 7 is a driving circuit, and 8 is a driving circuit. It is a temperature control element. The optical output of the semiconductor laser 1 is transmitted through a lens 2 and an optical isolator 3 to an optical branching component 4.
Is incident on. In the optical branching component 4, the incident light is branched into two, one is output as output light 100 of the frequency stabilized light source, and the other is incident on the photodetector 6 via the absorption cell 5. The drive circuit 7 drives the semiconductor laser 1 and the temperature control element 8 such that the frequency of the output light 100 matches the absorption line of the absorption cell 5 from the output of the photodetector 6.

[0003]

However, the oscillation frequency of the semiconductor laser 1 changes depending on the current and temperature, and the current coefficient and temperature coefficient of the oscillation frequency also change depending on the material, structure, and the like. Therefore, in the conventional example, control parameters of a drive circuit for driving the semiconductor laser and the like are set corresponding to each semiconductor laser. Therefore, for example, every time a semiconductor laser is replaced, it is necessary to reset control parameters such as a set current and a set temperature of a drive circuit each time. Therefore, an object of the present invention is to realize a frequency stabilized light source that does not require setting of control parameters such as a drive circuit when replacing a laser or a temperature control element.

[0004]

In order to achieve the above object, the present invention has a frequency discriminating element, and stabilizes the frequency by controlling the frequency of a laser light source to a specific frequency of the frequency discriminating element. A laser module comprising a laser, a temperature control element, and a storage element, a branching unit for branching the optical output of the laser module into two, and a frequency discrimination for receiving the optical output of the branching unit. An element, a photodetector that receives the optical output of the frequency discriminating element, and a drive circuit that drives the laser and the temperature control element based on a control constant and an output of the photodetector stored in the storage element. An operation control circuit for reading out the control constant stored in the storage element in accordance with an instruction from the drive circuit and transmitting the control constant to the drive circuit as initial setting information; It is characterized in that the.

[0005]

The drive circuit is driven by a control current or the like appropriately corresponding to each semiconductor laser or the like in accordance with various parameters due to differences in characteristics of each semiconductor laser or the like stored in the storage element in the laser module.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.
FIG. 1 is a configuration block diagram showing a first embodiment of a frequency stabilized light source according to the present invention. Here, 1 to 6 and 8 are given the same reference numerals as in FIG. In FIG. 1, 7a is a drive circuit, 9 is a storage element storing a set current, a set temperature, and the like, and 10 is an arithmetic control circuit having a function of transmitting setting information to the drive circuit 7a, a sequence control function, and the like.
Further, a semiconductor laser 1, a lens 2, an optical isolator 3,
The temperature control element 8 and the storage element 9 are the laser module 5
0.

[0007] The optical output of the semiconductor laser 1 is incident on an optical branching component 4 via a lens 2 and an optical isolator 3. In the optical branching component 4, the incident light is branched into two, one is output as output light 100 of the frequency stabilized light source, and the other is incident on the photodetector 6 via the absorption cell 5. The semiconductor laser 1 and the temperature control element 8 are driven such that the frequency of the output light 100 matches the absorption line of the absorption cell 5 by the output of the photodetector 6. At this time, the frequency of the output light 100 is
It is necessary to know the set current and the set temperature of the semiconductor laser 1 in advance in order to match the absorption line. In addition, in order to appropriately set the gain and the like of the circuit, it is necessary to know the current coefficient and the temperature coefficient of the frequency of the semiconductor laser 1 and the frequency characteristics at the time of current modulation.

Therefore, the arithmetic and control circuit 10 includes the drive circuit 7a
The set current, set temperature, and the like are read from the storage element 9 in accordance with the instruction, and are sent to the drive circuit 7a as initial setting information.
The drive circuit 7a operates based on the initial setting information such as the set current and the set temperature from the arithmetic and control circuit 10 so that the frequency of the output light 100 matches the absorption line of the absorption cell 5 based on the output of the photodetector 6. 1 and the temperature control element 8 are driven.

Here, when the laser module 50 is replaced, various parameters due to differences in characteristics of the individual semiconductor lasers 1 and the like are stored in the storage element 9 in the laser module 50.
The driving circuit 7a does not need to change any setting from the outside, and various parameters are read out by the arithmetic control circuit 10 and the driving circuit 7a is used as initial setting information.
, The adjustment is automatically performed, and the drive circuit 7a can be driven by a control current or the like appropriately corresponding to the semiconductor laser or the like of the replaced laser module 50.

FIG. 2 is a block diagram showing the configuration of a second embodiment of the frequency stabilized light source according to the present invention. Here, 1 to 4, 6, 8 to 10 and 50 have the same reference numerals as in FIG. In FIG. 2, 5a is an etalon as a frequency discriminating element, 7b is a drive circuit, and 11 is an etalon 5a.
Control element. The difference from FIG. 1 is that the interval between the etalons 5a is controlled by the control element 11. Here, the set value is sent from the arithmetic and control circuit 10 to the control element 11.

For example, when the interval of the etalon 5a is thermally controlled, the setting conditions of the control element
When the distance between the etalons 5a is controlled by using the piezoelectric element as a piezoelectric element, the driving conditions are stored in correspondence with the individual semiconductor lasers 1, respectively. As a result, the driving circuit 7b does not need to change any setting from the outside, and various parameters are read out by the arithmetic and control circuit 10 and are sent to the driving circuit 7b as initial setting information, so that the adjustment is automatically performed. 7b can drive the semiconductor laser 1 and the control element 11 with a control current or the like appropriately corresponding to the semiconductor laser or the like of the replaced laser module 50.

Further, by using the laser module 50, since it does not depend on the characteristics of individual semiconductor lasers or the like in the laser module 50, it can be applied to a frequency stabilized light source having a plurality of lasers. FIG. 3 is a structural block diagram showing a third embodiment of the frequency stabilized light source according to the present invention. Here, 1 to 10, 50 and 100 are denoted by the same reference numerals as in FIG. In FIG. 3, 1a is a semiconductor laser, 2a is a lens, 3a is an optical isolator, 4a
Is an optical branching component, 6a is a photodetector, 7c is a drive circuit, 8a
Is a temperature control element, 9a is a storage element storing a set current, a set temperature, etc., 12a and 12b are mirrors, 13 is an optical branching component, and 200 is output light. In addition, the semiconductor laser 1
a, lens 2a, optical isolator 3a, temperature control element 8
a and the storage element 9a constitute a laser module 50a.

The operation of the control loop constituted by the laser module 50 is the same as that of the embodiment shown in FIG. The output light of the laser module 50a is divided by the optical branching component 4a into two.
And one is output light 200 of the frequency stabilized light source.
And the other is incident on the optical branching component 13 via the mirror 12a. In the optical branching component 13, the output light 100
And 200 are multiplexed and incident on the photodetector 6a. The drive circuit 7c drives the semiconductor laser 1a and the temperature control element 8a so that the frequency of the beat signal generated by the multiplexing becomes an arbitrary constant value. At this time, the arithmetic and control circuit 10 reads the set current, the set temperature, the current coefficient of the frequency, and the like from the storage element 9a in accordance with the instruction of the drive circuit 7c, and sends it to the drive circuit 7c as initial setting information. The drive circuit 7c drives the semiconductor laser 1a and the temperature control element 8a so that the frequency of the output light 200 becomes an arbitrary constant value based on the output of the photodetector 6a based on the initial setting information from the arithmetic control circuit 10.

According to the third embodiment shown in FIG.
Output light 200 having the same frequency stability as 00 and having an arbitrary frequency can be obtained.

Further, the light emitting source is not limited to a semiconductor laser, and another laser may be used. Further, as the storage element 11, a ROM (Read Only Memory), a RAM (Random Acce
In addition to a semiconductor memory such as an ss memory, a resistance value of a resistance element may be used, or a magnetic storage element such as a magnetic bubble may be used.

[0016]

As is apparent from the above description,
According to the present invention, the following effects can be obtained. Various parameters due to differences in characteristics of individual semiconductor lasers are stored in the storage element in the laser module, and the drive circuit is controlled by these parameters, so that the control parameters of the drive circuit etc. are set when the semiconductor laser is replaced. Becomes unnecessary.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram showing a first embodiment of a frequency stabilized light source according to the present invention.

FIG. 2 is a configuration block diagram showing a second embodiment of the frequency stabilized light source according to the present invention.

FIG. 3 is a configuration block diagram showing a third embodiment of the frequency stabilized light source according to the present invention.

FIG. 4 is a configuration block diagram showing an example of a conventional frequency stabilized light source.

[Explanation of symbols]

 Reference Signs List 1, 1a Semiconductor laser 2, 2a Lens 3, 3a Optical isolator 4, 4a, 13 Optical branching component 5 Absorption cell 5a Etalon 6, 6a Photodetector 7, 7a, 7b, 7c Driving circuit 8, 8a Temperature control element 9, 9a storage element 10 operation control circuit 11 control element 12a, 12b mirror 50, 50a laser module 100, 200 output light

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-4-225584 (JP, A) JP-A-3-196589 (JP, A) JP-A-2-20084 (JP, A) JP-A-5-2008 3361 (JP, A) JP-A-5-159092 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01S 3/18 H01S 3/133 JICST file (JOIS)

Claims (1)

(57) [Claims] 1. A frequency stabilizing light source having a frequency discriminating element and controlling the frequency of a laser light source to a specific frequency of the frequency discriminating element to stabilize the frequency, wherein the laser includes a laser, a temperature control element, and a storage element. A module, branching means for branching the optical output of the laser module into two, a frequency discriminating element for receiving the optical output of the branching means, and a photodetector for receiving the optical output of the frequency discriminating element. A drive circuit for driving the laser and the temperature control element based on a control constant stored in the storage element and an output of the photodetector; and a drive circuit stored in the storage element according to an instruction from the drive circuit. A frequency control light source comprising: an arithmetic control circuit that reads out a control constant and sends the control constant to the drive circuit as initial setting information.