JPH05343809A - Semiconductor laser device system - Google Patents

Abstract

PURPOSE:To make the life of a semiconductor laser long and to enhance the operating reliability of a system using it as a light source by a method wherein individual laser resonators are driven respectively independently as currently used ones and as spare ones and, when a currently used laser resonator is deteriorated, it is changed over sequentially to a spare laser resonator. CONSTITUTION:A drive changeover means 3 drives and stops a currently used laser resonator on the basis of an instruction signal which is output from a deterioration detection means 2. It changes over and drives a spare laser resonator in the remaining part according to the predetermined order of priority. It is used as a new currently used laser resonator. For example, a laser resonator which includes a second stripe region 16 is used as a currently used laser resonator. Concretely, a driving electric-power changeover circuit 3 which supplies electric power to electricity-feeding terminals 18a to 18c as driving parts for individual laser resonators is used, and the supply drive parts are changed over by timing that a deteriorated laser resonator does not radiate a beam. Since spare parts are assembled in a semiconductor laser 1 itself in this manner, the constitution of a device is simplified, and a laser beam can be radiated for a long time and stably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device system including a multi-beam semiconductor laser.

[0002]

2. Description of the Related Art Semiconductor lasers are often used as light sources for optical information processing systems such as optical disks and laser printers, or optical communication systems. In the semiconductor lasers for these applications, the laser beam can be turned on / off simply by changing the injection current, so that the configuration of these systems can be simplified.

By the way, since the life of a semiconductor laser changes depending on the driving frequency, its output level, the ambient temperature, etc., it is impossible to predict this completely, and it is the present condition that it can be known only after actually using it. is there. Therefore, the reliability of the semiconductor laser may be the lowest among the components of the system. In this case, the reliability of the semiconductor laser determines the reliability of the system.

Therefore, conventionally, the system side is provided with a laser beam output decrease detection means and a threshold current increase detection means, and it is determined that the semiconductor laser has reached the end of its life when each detected value exceeds a certain allowable range. I am trying to give an abnormal display. At this time, human beings dealt with it by exchanging it with a normal semiconductor laser.

[0005]

However, since the system is provided with precision-positioned optical systems, it is usual to perform alignment with these optical systems when exchanging the semiconductor laser. , Had the problem of spending a great deal of time. Further, the decrease in the output level of the laser beam and the increase in the threshold current may not always be due to the life. A similar phenomenon occurs even if the temperature changes due to thermal crosstalk, for example. Therefore, an error occurs in the life detection,
The semiconductor laser may be replaced unnecessarily.

On the other hand, in the case of a system using low-reliability parts, it is generally practiced to incorporate a spare part of the same standard as the current part in order to achieve high reliability.
However, in the case of a system using a semiconductor laser, the arrangement of the optical system is delicate, and it is necessary to prepare a dedicated optical system in order to incorporate the spare parts, which is extremely expensive.

The present invention has been made in view of such a background, and an object thereof is to provide a semiconductor laser device system capable of constructing an inexpensive and highly reliable system.

[0008]

The semiconductor laser device system of the present invention utilizes the characteristics of a multi-beam semiconductor laser and incorporates a spare part into the semiconductor laser itself to solve the above problems.

Specifically, a semiconductor laser in which a plurality of laser resonators each having an independent drive structure are closely formed in a laser chip, deterioration detecting means for detecting deterioration of a specific laser resonator of the semiconductor laser, and A semiconductor laser device is configured to have drive switching means for switching driving of the laser resonator, and at least one of these laser resonators is switched by the drive switching means when deterioration of the laser resonator during driving is detected. The backup laser resonator is used.

In this case, the deterioration detecting means is
Photodetection photodiode provided near the laser that monitors the output level of the driving laser beam, or
A power detection circuit for detecting an electromotive force between the energizing terminals of the auxiliary laser resonator adjacent to the driven laser resonator, or a voltage when a reference current is applied to the undriven auxiliary laser resonator. It is composed of a voltage detection circuit for detecting. The drive switching means stops driving the laser resonator being driven based on the detection signal output from the deterioration detecting means, and drives the remaining laser resonators in a switching order according to a predetermined priority. It is composed of a switching circuit.

[0011]

The standby laser resonator is not driven during normal use, but functions as a monitor for the laser resonator during driving. That is, in a multi-beam semiconductor laser in which the laser resonators are optically strongly coupled, the auxiliary laser resonator adjacent to the one being driven acts as a photodiode. Therefore, the laser beam output during driving can be known by detecting the electromotive force.

Further, the thermal resistance of the preliminary laser resonator increases due to the influence of heat generated in the driving laser oscillator. Therefore, the heat rise of the laser chip can be indirectly detected by measuring the voltage when the reference current flows and detecting the resistance value. Further, when there are a plurality of spare laser resonators, the priority order is determined, and switching is performed in this order, whereby the drive switching is smoothly performed.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a semiconductor laser device according to an embodiment of the present invention.
Is composed of, for example, three laser resonators whose oscillation region is the current-carrying region of the active layer 13 sandwiched between the cladding layers 12 and 14 on the substrate 11, and is packaged at the time of use.

When a current is passed from the current-carrying terminals 18a to 18c toward the common current-carrying terminal 10 during driving of these laser resonators, the carriers passing through the contact layers 17a to 17c become
It moves to the cladding layer 14 through the gap between the current blocking layers 15a to 15d. At this time, the carriers are distributed in a beam shape from the cladding layer 14 to the common current-carrying terminal 10 due to the electric field, and the width across the active layer 13 depends on the widths of the stripe regions 16a to 16c, respectively. Then, the regions of the active layer 13 corresponding to these widths oscillate and emit laser beams respectively. The beam interval between these laser beams is 15 [μm].

In the present embodiment, in the above-described structured semiconductor laser, a resonator including the first stripe region 16a is used as a working laser resonator, and second and third stripe regions 16b are used.
Each of the resonators including 16c is used as a spare laser resonator, and the beam emitted from the current one is used as the light source of the laser printer.

The deterioration detecting means 2 is a semiconductor laser 1.
This is for detecting the deterioration of the working laser resonator, and has a power detection circuit for detecting an electromotive force generated in an adjacent spare laser resonator. This is because, in a semiconductor laser having a structure in which a plurality of laser resonators are optically strongly coupled as shown in FIG. 1, an undriven laser resonator adjacent to a driven one functions as a photodiode. Therefore, the laser beam output during driving can be known by detecting the electromotive force. In this case, the voltage generated in the active layer of the laser resonator during driving is constant regardless of the beam intensity, but by shunting with a resistor of an appropriate value, the voltage is generated in the cladding layer of the preliminary laser resonator. The voltage that occurs between the energized terminals due to the drop is a function of the beam intensity during driving. Therefore, when the electromotive force falls below the predetermined allowable range, it is determined that the working laser resonator has reached the end of its life, and a command signal is output to the drive switching means 3 described later.

Further, the deterioration detecting means 2 has a voltage detecting circuit for detecting a voltage when a reference current is passed through an undriven spare laser resonator. This focuses on the fact that the thermal resistance of the standby laser resonator increases due to the effect of heat generated in the laser oscillator during driving. That is, by measuring the voltage when the reference current is passed and detecting the resistance value at that time,
The heat rise of the laser chip can be indirectly detected. As a result, it becomes easy to make a comprehensive judgment as to whether the reduction in the output level of the laser resonator during driving is due to life or heat generation. Therefore, it is possible to avoid a situation in which the command signal is erroneously issued.

The deterioration detecting means 2 can also be realized by using an ordinary photodiode. In this case, a photodiode is provided in the package of the semiconductor laser and the slope rate of the current laser resonator is measured at any time. Then, for example, when the slope rate at the time of measurement reaches about 80% of the initial slope rate, the life is determined, and a predetermined binary signal is output to the drive switching means 3.

The drive switching means 3 stops driving the active laser resonator based on the command signal output from the deterioration detecting means 2 and switches the remaining spare laser resonators in accordance with a predetermined priority. , This is the new working. For example, in FIG. 1, a laser resonator including the second stripe region 16b is used as an active part. Specifically, the drive switching means 3 uses a drive power switching circuit that supplies power to the drive section of each laser resonator, and the supply drive section is controlled by observing when the deteriorated laser resonator is not emitting a beam. Switch.

Although the position of the laser beam after switching is separated by about 15 [μm] from that before switching, the position can be adjusted even if the mounting portion of the semiconductor laser deviates by about 30 [μm]. By configuring the optical system, it is possible to cope with the current / standby switching. Further, when the laser resonator newly switched to the current one also deteriorates, the remaining laser resonator is switched to the current one, and when this also deteriorates, the life of the semiconductor laser is reached.

As described above, in this embodiment, the spare parts are incorporated in the semiconductor laser 1 itself, so that the device structure is simplified. Moreover, since the laser beam can be emitted stably for a long period of time, a laser printer using this device as a light source can be manufactured at low cost, and its operation reliability is significantly improved as compared with the conventional one.

In the present embodiment, an example using a semiconductor laser having three laser resonators has been described.
The present embodiment can be realized if the working and spare laser resonators are provided, and the number is not necessarily limited to this number. Further, it can be applied to optical information processing systems other than laser printers and optical communication systems. Also,
In the present embodiment, the spare laser resonator was used as a backup and monitor (sensor) for current use, but it can be used only as a monitor.

[0024]

As described above in detail, in the present invention, a semiconductor laser in which a plurality of laser cavities each having an independent drive structure are formed in a laser chip is used, and each laser cavity is used as a working or a standby respectively. The semiconductor laser is driven independently, and when the current one is deteriorated, the spare laser is sequentially switched to the spare. Therefore, the life of the semiconductor laser is significantly extended, and the operation reliability of the system using this as a light source is improved. in this case,
Since the oscillation regions of the laser resonators are close to each other, switching can be performed with a slight position adjustment, and it is not necessary to provide a spare optical system. Therefore, an inexpensive and highly reliable system can be easily constructed.

Further, according to the present invention, since the deterioration detecting means for detecting the deterioration of the specific laser resonator and the drive switching means for switching the driving of each laser resonator are provided, the active / standby switching can be facilitated. It can also be automated. Therefore, it is not necessary to stop the system at the time of switching, and the operation reliability can be further enhanced. The deterioration detecting means is a power detection circuit for detecting an electromotive force generated in a spare laser resonator adjacent to the active laser resonator, and a voltage detection circuit for detecting a voltage when a reference current is passed through the spare laser resonator. Therefore, deterioration can be easily detected, and a detection error due to heat generation can be eliminated.

Further, during the current deterioration, the drive power supplied to the drive unit of the remaining spare laser resonator is sequentially switched in accordance with a predetermined priority order, so that the drive switching timing can be easily set and the switching is made. Can be done quickly.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a semiconductor laser device according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser, ... Deterioration detection means, 3 ... Drive switching means, 10 ... Common energization terminal, 11 ... Semiconductor substrate, 12, 1
4 ... Cladding layer, 13 ... Active layer, 15a to 15d ... Current blocking layer, 16a to 16c ... Stripe region, 17a
.About.17c ... contact layer, 18a.about.18c ... current-carrying terminal (laser resonator drive section).

Claims (4)

[Claims] 1. A semiconductor laser in which a plurality of laser cavities each having an independent drive structure are closely formed in a laser chip, deterioration detecting means for detecting deterioration of a specific laser cavity of the semiconductor laser, and each laser resonator. Drive switching means for performing switching drive of, and at least one of these laser resonators,
A semiconductor laser device system comprising: a standby laser resonator that is switched and driven by the drive switching means when deterioration of the laser resonator is detected during driving. 2. The deterioration detecting means includes a power detection circuit for detecting an electromotive force between current-carrying terminals of the auxiliary laser resonator adjacent to a laser resonator being driven. The semiconductor laser device system described. 3. The semiconductor laser device system according to claim 1, wherein said deterioration detecting means includes a voltage detecting circuit for detecting a voltage when a reference current is passed through said undriven spare laser resonator. .. 4. The drive switching means stops driving the laser resonator being driven based on a command signal output from the deterioration detecting means, and switches the remaining spare laser resonators according to a predetermined priority order. 2. The semiconductor laser device system according to claim 1, wherein the semiconductor laser device system is a drive power switching circuit for driving.