JPS63314877A - Semiconductor laser light source - Google Patents

Abstract

PURPOSE:To reduce the size of a laser light source and to control it at a suitable temperature by using a light quantity photodiode as a light quantity monitor and a temperature sensor in a time sharing manner. CONSTITUTION:A timing circuit 12 transmits control signals S1-S3 of predetermined phase relationship to switch means 7, holding circuits 8, 9, respectively. When the signal S1 is 'H', the circuit 9 inputs the output of an I/V converter 6 at the time of the rising edge of the signal S1 and holds it. When the signal S2 is 'H', the circuit 8 inputs the output of an amplifier 5 at the time of the rising edge of the signal S2, and holds it. The means 7 is closed during the 'H' of the signal S3. The control is conducted at this timing to use a light quantity monitor photodiode PD2 as a light quantity monitor and a temperature sensor in a time sharing manner.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to means for stabilizing the humidity and output sales area of a semiconductor laser light source.

(Prior Art) The life of a semiconductor laser diode (hereinafter simply referred to as LD) is affected by temperature. This will be explained using Fig. 4. Fig. 4 shows the current-light output characteristics of the LD. The parameter T shown in the figure represents the temperature, and the temperature value is
t, < t2 < t3. As can be seen from the figure, when obtaining the output light ff1p+, the higher the temperature, the larger the current must be applied to the LD. As a result, the life of the LD is shortened in high temperature conditions. Therefore, the temperature of the package provided with the LD is adjusted.

Also, when controlling the output laser wavelength to a certain value, it is necessary to control the temperature of the semiconductor laser diode, so the temperature of the LD is detected and measured.

[Problem that the invention seeks to solve]

In order to control the temperature of a package provided with an LD, it is necessary to attach a temperature sensor to the package to detect the temperature.

FIG. 3 is a diagram showing a conventional temperature detection means.

In the same figure, 1 is an LD, 3 is a package in which the LDI is incorporated, 21 is a plate to which package 3 is attached,
22 is a heat capacity body provided in close contact with the plate 21;
3 is a temperature sensor embedded in the heat capacitor 22.

The temperature sensor 23 cannot accurately measure temperature unless it has a general heat capacity.
As shown in FIG. 3, it is embedded in the heat capacity body 22 and attached to the third part of the package.

As a result, the shape of the conventional semiconductor laser light source to which the temperature sensor 23 is attached becomes undesirably large.

An object of the present invention is to provide a semiconductor laser light source that can control the fAa of the LD by detecting the temperature of the LD without providing a special external temperature sensor, and can also control the amount of output light.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention provides a semiconductor laser diode including a photodiode for monitoring light intensity in the same package, means for heating and cooling the package, and detecting the open circuit voltage of the photodiode for monitoring light intensity. and a means for controlling the heating/cooling means based on this n discharge voltage; and means for detecting the F:J circuit lightning current of the light amount monitoring photodiode, and determining the current value to be passed through the semiconductor laser diode based on this short circuit current. ! 2III, and a timing circuit for controlling the detection of the open circuit voltage of the photodiode for monitoring the amount of light and the detection of the short circuit current in a time-division manner.

(Example) Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a diagram showing an example of an actual droplet of a semiconductor laser light source according to the present invention.

In the figure, 1 is a semiconductor laser diode (LD)
, 2 is a light intensity monitoring photodiode (hereinafter referred to as PD) provided in the same package 3 as LDl.
One terminal of Dl and PD2 is commonly connected to circuit ground.

4 is a heating/cooling device provided in the third part of the package;
It heats and cools the package 3 (also known as LDl) below the temperature controller ll1lJ Ill, which will be described later.

Reference numeral 5 denotes an amplifier that receives the open-circuit voltage v0 of the PD 2, and here it is constituted by a voltage follower circuit having high input impedance characteristics.

6 is an I/■ converter, and the short-circuit current 1s1F of PD2 introduced through the switch means 7! : Converts to voltage value.

Reference numeral 7 denotes a switch means, which is controlled by a control signal S applied from a timing circuit, which will be described later, and can be constituted by, for example, an analog switch.

8.9 is a hold circuit, and the hold circuit 8 receives a control signal S2 applied from a timing circuit to be described later.
PD2 introduced via the amplifier 5 during the period “gh”
It holds the open circuit voltage of and outputs the signal Sb to the next stage. Note that during the period when the control signal S2 is "low", the output S8 of the amplifier 5 is output as is.

In addition, the hold circuit 9 operates during the period when the control signal S1 applied from the timing circuit described later is "old gh".
(2) It holds the output SA of the converter 6 and outputs the signal Sa to the next stage. Note that the control signal S+ is “toy”
During the period , the output SA of the converter 6 is output as is.

A temperature controller 10 controls the heating/cooling device 4 based on the signal Sb introduced from the hold circuit 8 to control the temperature of the package 3 to a desired temperature. Note that a publicly known temperature controller 10 can be used.

Reference numeral 11 denotes a current regulator, which controls lightning current to flow through the LDl based on the signal Sa introduced from the hold circuit 9 so that a desired output light amount is obtained. Incidentally, a known one can be used as this current generator 11.

A timing circuit 12 controls the operation timing of the switch means 7 and the hold circuits 8 and 9.

The features of the present invention will be described. In commercially available semiconductor laser diodes, a photodiode for monitoring the amount of light is usually provided in the same package in order to monitor the amount of light output from the LDI. The present invention is characterized in that the photodiode for monitoring the amount of light is used for time-divisionally using the photodiode for monitoring the amount of light and for the temperature sensor of the LDI.

The operation of the apparatus shown in FIG. 1 will be explained below with reference to the time chart shown in FIG.

FIG. 5 shows an example of the appearance of a common commercially available LD1. In FIG. 5, 3 is a package, which has a cylindrical shape in FIG. 5 and forms a small space with the plate 21. In FIG. An LDl attached to the member 3b is provided in this space. Then, the transparent cover 38 is attached to the package 3.
is provided on the front of the LDI through this transparent cover 3a.
is irradiated with an output laser beam. Also, in Figure 5,
Although hidden from view, a photodiode PD2 for monitoring the amount of light is provided in the space formed by the package 3 and the plate 21 to monitor the amount of light output from the LD1.

In addition to FIG. 1, the timing circuit 12 is shown in FIG. 2 (1).
and the control signal QS+ having the phase relationship shown in (3) and (6).

82.33 is added to the switch means 7 and the hold circuit 8.9.

When the control signal S is "old gh", the hold circuit 9
is ■・V when the rising edge of control signal S occurs.
Take in the output S^ (see Fig. 2 (2)) of the converter 6 and hold it during the “high” period (see Fig. 2 (4)).
)reference).

On the other hand, when the control signal $2 is "high", the hold circuit 8
is the output of the amplifier 5 when the rising edge of the control signal S2 occurs (corresponds to the IFfl discharge voltage ■0...Fig. 2 (5)
) self-illumination) and hold it during the period of "high".

Further, during the period when the control signal S3 is "high", the switch means 7 is turned on.

By controlling at such timing, the photodiode PD2 for monitoring the amount of light can be used in a time-sharing manner for monitoring the amount of light and for use as a temperature sensor. The operation will be explained below.

In FIG. 2, at time t1, the switch means 7 is on;
Hold circuit 8 is in a hold state, and hold circuit 9 is in a through state. Since the switch means 7 is on, P
O2 open circuit voltage V. is the virtual ground potential of the amplifier U that constitutes the I/■ converter 6, which is Qv (see Figure 2 (5)). (A) At time t2, when the Ill flit signal S1 rises (see (3) ), I when this rising edge occurs
・■The hold circuit 9 holds the value of the output S^ of the converter 6 (see FIG. 2 (4)). Then, the W flow regulator 11 takes in this held 1lfIS a, and this signal S
Based on a, the current flowing through the LDl is set by iil1wJ to control the amount of output light.

(B) At time t3, the switch means 7 is turned off. Therefore,■
・The output of the V converter 6 becomes O■ (see Figure 2 (2))
At the same time, the open-circuit voltage V0 of PO2 reaches a value of 2, so the output Sa of the amplifier 5 changes as shown in FIG. 2 (5). Then, when the control signal S2 becomes "10W" at time t4, the output Sb of the hold circuit 8 changes as shown in FIG. 2 (7), and when the control signal S2 rises at time t5, this rising edge occurs. The value of the output Ss of the amplifier 5 at the time (t5) is held.The temperature controller 10 takes in this held value Sb, and controls the heating/cooling device 4 based on this signal Sb to adjust the temperature of the package 3. Set it to the desired value.

Thereafter, since the switch means 7 is turned on again at time t6, the short circuit current Is of PO2 flows into the I/■ converter 6 again (see Fig. 2), and the open circuit voltage Vo is
(see FIG. 2 (5)), and returns to the same state as at time t1.

As described above, in the present invention, the short-circuit current Is of PO2 is voltage-converted and introduced into the current regulator 11 as the hold circuit output voltage, and the amount of output light is controlled by adjusting the current flowing through the LDI.

On the other hand, regarding the measurement of the temperature of LDl, the open circuit voltage vO of PD2 is measured by the amplifier 5, and the hold circuit output voltage Sb
The temperature of the LDl is controlled to a desired value by introducing it into the temperature regulator 10 and controlling the heating/cooling device 4.

Note that the short circuit current Is of PD2 is a function of only the light 1, and the open circuit voltage V0 is a function of the amount of light and temperature. In the present invention, the short circuit current Is is detected and fed back to stabilize the amount of light, so the open circuit voltage vo can be regarded as a function only of temperature. The reason for this will be explained in detail.

Although not shown in the drawings, it is generally known that a photodiode is represented by a parallel circuit consisting of a constant current source A through which a photocurrent IL proportional to the amount of irradiated light flows and a diode d. Therefore, the short #Ij current Is of PD2
is the current TL of one shift according to the amount of light.

Also, the open circuit voltage of PD2 ■. is expressed by the following equation.

Vo'#i'u (Yu L + 1) Earthwork e1 nail: Boltzmann constant e: ゛ Ti charge of electron T: Absolute temperature of PD2 ■ = Current generated by incident light I Top: Bright current (function of temperature) Here If the incident light is constant, Vo, CTe T (CT: m degree coefficient)
It can be done.

Note that from the above equation, the open circuit voltage VO has a temperature coefficient of about -2 mV/, and the present invention uses this to detect the temperature.

[Effects of the present invention]

As described above, according to the present invention, the following effects can be obtained.

■ Since no special external temperature sensor is required, the semiconductor laser light source can be made smaller.

(2) Since the PD2 is in the same package as the LD chip, it can measure a value closer to the LD chip temperature than an external sensor, and can perform appropriate temperature control.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the configuration of a semiconductor laser light source according to the present invention, FIG. 2 is a time chart of signals of each part of the device shown in FIG. 1, FIG. 3 is a diagram showing the configuration of conventional means, and FIG. A diagram showing the relationship between current and optical output of a semiconductor laser diode, and FIG. 5 is a diagram showing an example of the appearance of a commercially available semiconductor laser diode. 1...LD, 2...PD, 3...package, 4
...Heating/cooler, 5...Amplifier, 6...I-■
Converter, 7... Switch means, 8.9... Hold circuit, 1 (>... Temperature regulator, 11... Current regulator, 12... Timing circuit. Fig. 1 Fig. 3 4th ploy 5 ahead 5th peso push 1 J 21/3b LD 咎Pu

Claims (1)

[Scope of Claims] A semiconductor laser diode including a photodiode for monitoring the amount of light in the same package, means for heating and cooling the package, detecting an open circuit voltage of the photodiode for monitoring the amount of light,
means for controlling the heating/cooling means based on the open circuit voltage; and detecting the short circuit current of the light amount monitoring photodiode;
means for controlling the value of current flowing through the semiconductor laser diode based on the short-circuit current; detecting the open circuit voltage of the photodiode for monitoring the amount of light;
A semiconductor laser light source comprising: a timing circuit that controls short-circuit current detection in a time-sharing manner; and a semiconductor laser light source.