JPH03259584A - Semiconductor laser apparatus - Google Patents

Abstract

PURPOSE:To enhance a modulation speed by a method wherein one electrode of a laser is connected to a metal case via a second conductor pattern and an inductive element and the other electrode is connected to the metal case via a capacity element and a first conductor pattern from the second conductor pattern. CONSTITUTION:A coaxial cable is connected to a coaxial connector 19; a modulation signal transmitted through its core part is input to a laser driving gear 22 via an axis (b), a third conductor pattern (f) and a bonding wire 23. The gear 22 changes an injection current into a laser 11 according to an input signal. The injection current is supplied to one electrode of the laser 11 via a bonding wire 24. When a shielding wire of the coaxial cable is set as a ground line, a metal case 13 can be grounded by connecting the coaxial cable to the coaxial connector 19. At this time, the other electrode of the laser 11 is connected to the case 13 via a second conductor pattern (e) and an inductive element line 25; grounded at a low impedance and a laser beam can be modulated at high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention (Industrial Application Field) This invention relates to a semiconductor laser device mainly used as a light source of a gigabit band optical communication device.

(Prior Art) Conventionally, in optical communications, efforts have been made to increase the transmission speed in order to make transmission paths more economical, and it is now possible to transmit several gigabits per second. A semiconductor laser device is mainly used as a light source. Regarding the semiconductor laser mounted in this device, one with a modulation band exceeding 10 gigahertz has also been developed. As the speed of optical communication continues to increase, modularization technology is important to put it into practical use. In particular, since the optical output of a semiconductor laser increases as the speed increases, it is necessary to improve reliability and stabilize the optical output by using a Vertier element or the like. Along with such mounting technology, technology for supplying high-speed signals to semiconductor lasers is also important.

A conventional semiconductor laser device generally has a structure as shown in FIG. In FIG. 2, reference numeral 11 denotes a semiconductor laser, and this semiconductor laser 11 is mounted on an electrode surface a of a base 12 made of a Beltier element (hereinafter referred to as a Peltier element base), and housed in a metal case 13. A signal human power lead 14 is attached to the metal case 13 via an insulating element 15, and an optical fiber 16 is attached so that its tip is located near the light emission position of the semiconductor laser.

This tip is generally tapered. The electrode surface a of the Peltier element stand 12 is connected to the metal case 1
3 by a bonding wire 17, thereby connecting the metal case 13 and one electrode of the semiconductor laser 11. Further, the other electrode of the semiconductor laser 11 is connected to the signal human power lead 14 via a bonding wire 18.

That is, since one electrode of the semiconductor laser 11 is grounded to the metal case 13 via the bonding wire 17 on the electrode surface a1 of the Peltier element stand 12, the modulation signal manually input from the lead 14 is transmitted to the semiconductor laser via the bonding wire 18. When power is supplied to the other electrode of the laser 11, the oscillation wavelength of the semiconductor laser 11 changes according to the change in the injected current, and the laser beam corresponding to the modulated signal is transmitted to the optical fiber 1.
It begins to radiate towards 6. At this time, the semiconductor laser 11 generates heat as the laser beam is emitted, but this heat is absorbed by the Peltier element base 12 and radiated to the metal case 13.

By the way, in the conventional semiconductor laser device with the above configuration, the leads and bonding wires are long, so relatively little heat is transmitted through this path, and the Peltier element stand can sufficiently block the heat conduction, and the semiconductor laser and the metal case can be separated. It is possible to ensure a sufficient temperature difference between On the other hand, it becomes difficult for high-speed electrical signals to be transmitted, with the limit being about 2 gigabits per second.

Even if it were possible to shorten the leads and bonding wires, the Peltier element stand would not be able to absorb enough heat, and the thermal resistance between the semiconductor laser and the metal case would become low, making it insufficient to maintain the temperature difference. It becomes.

(Problems to be Solved by the Invention) As stated above, in the conventional semiconductor laser device,
It has been extremely difficult to achieve both high-speed modulation on the order of gigabit or higher and thermal stability.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a semiconductor laser device that is thermally stable and can dramatically improve the modulation speed.

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, a semiconductor laser device according to the present invention includes a semiconductor laser having electrodes on surfaces facing each other, and a conductor pattern formed on the front and back surfaces. , a substrate on which the semiconductor laser is placed and fixed; a Peltier device stand on which one end of the substrate is placed and fixed; the semiconductor laser, the substrate, and the Peltier device stand are housed;
a metal case formed therein with a beam having the same height as the Peltier element stand and on which the other end of the substrate is placed and fixed; a coaxial connector in which a coaxial line to which a modulated signal transmission line of the cable is connected protrudes, and which is electrically connected to a surrounding metal case to which a shielded line, which is a reference potential line of the coaxial cable, is connected; an optical fiber cable that is attached to the metal case and has a tip of the optical fiber line located at a laser beam emission position of the semiconductor laser, and the conductor pattern formed on the substrate includes at least a first conductor pattern formed on the back surface. It consists of a first conductor pattern, a second conductor pattern connected to the front and back surfaces, and a third conductor pattern formed on the front surface, and the first conductor pattern is in contact with the beam and electrically conductive. The second conductor pattern is formed to be in contact with the Peltier element base and to be electrically connected to one electrode of the semiconductor laser, and the second conductor pattern is in contact with the Peltier element base and to be electrically connected to one electrode of the semiconductor laser. The pattern is formed close to the arrangement position of the coaxial and semiconductor lasers, the first and second conductor patterns are coupled to each other by a capacitive element, and the second conductor pattern is connected to the metal case via an inductive element. and the third conductive pattern is directly or indirectly connected to the other electrode of the coaxial and semiconductor laser.

(Function) In the semiconductor laser device having the above configuration, the metal case is connected to the shield wire of the coaxial cable through the coaxial connector and has a reference potential, and one electrode of the semiconductor laser is connected to the shield wire of the coaxial cable through the coaxial connector.
The conductor pattern is connected to the metal case via the inductive element, and the second conductor pattern is connected to the capacitive element and the metal case via the first conductor pattern, so it is grounded with sufficiently low impedance. That will happen.

On the other hand, the modulated signal sent through the coaxial line of the coaxial cable is transmitted through the coaxial line of the coaxial connector, via the third conductor pattern, to the vicinity of the semiconductor laser, and then directly or indirectly sent to the other electrode of the semiconductor laser. It will be done. Therefore, the semiconductor laser oscillates in response to the modulation signal and emits laser light. This laser light is input into an optical fiber and transmitted and output. At this time, the heat generated in the semiconductor laser is conducted to the Peltier element base through the second conductor pattern, but the second conductor pattern is connected to the metal case via an inductive element and a capacitive element. So,
Sufficiently large thermal resistance can be ensured between the semiconductor laser and the metal case.

(Embodiment) An embodiment of the present invention will be described below with reference to FIG. However, in FIG. 1, the same parts as in FIG. 2 are denoted by the same reference numerals, and the different parts will be mainly explained here.

FIG. 1 shows its configuration. A coaxial connector 19 is attached to the metal case 13 in place of the lead, and its ground side is directly screwed to the metal case 13 for electrical connection. is provided to protrude inside through the insulating member 15. The metal case 13 is formed so that the lower part of the coaxial frame inside thereof has the same height as the Peltier element stand 12. This part becomes the support base C.

A substrate 20 of an appropriate thickness is placed and fixed on the support stand C and the Peltier element stand 12.

On the lower surface of this substrate 20, a support stand C and a Peltier element stand 1 are provided.
2, the first and second conductor patterns d are separated from each other;
A capacitive element 21 is arranged and connected between these patterns d and e.

The end of the first conductor pattern d is electrically coupled to the Peltier element stand d of the metal case 13.

The second conductor pattern e is formed to extend further through the end surface to the end of the upper surface so as to be joined to the Peltier element base 12.

The semiconductor laser 11 is mounted on a conductive pattern e formed at an end of the substrate 20. A laser driving device 22 is mounted on the upper surface of this substrate 20 at a position close to the semiconductor laser 11, and a third conductor pattern f is formed from a position near this laser driving device 22 to a position where the coaxial plate is arranged. The third conductive pattern f and the coaxial line are directly connected, the third conductive pattern f and the signal input terminal of the laser driving device 22 are connected by a bonding wire 23, and the current output terminal of the laser driving device 22 and the semiconductor laser 11 through a bonding wire 24.

Further, on the lower surface side of the substrate 20, the second conductor pattern e and the metal case 13 are connected by an inductive element wire 25 made of a sufficiently long bonding wire or the like. An optical fiber 16 is located near the laser beam emission position of the semiconductor laser 11.
The tapered tip of the ball is located.

In the above configuration, the operation thereof will be explained below.

A coaxial cable (not shown) is connected to the coaxial connector 19, and the modulated signal transmitted through the core wire of this in-phase cable is sent to the laser driving device 22 via the coaxial b and third conductor pattern f1 bonding wires 23. is input.

This laser driving device 22 changes the current injected into the semiconductor laser 11 in response to a human power signal. This injection current is supplied to one electrode of the semiconductor laser 11 via the bonding wire 24.

On the other hand, if the shield wire of the coaxial cable is used as a ground line, the metal case 13 can be grounded by connecting this coaxial cable to one coaxial connector. At this time, the other electrode of the semiconductor laser 11 is connected to the metal case 13 via the second conductor pattern e and the inductive element wire 25, so that it is grounded with sufficiently low impedance. Furthermore, since the capacitive element 21 is connected to the support base C of the metal case 13 via the first conductor pattern d, it is grounded with low impedance in terms of alternating current as well.

Therefore, in the semiconductor laser device having the above configuration, the length of the bonding wire up to the semiconductor laser 11 is extremely short compared to the conventional one, and this enables high-speed modulation of laser light up to about 10 gigabits. Further, the heat generated by the semiconductor laser 11 is absorbed by the Peltier element stand 12 via the conductor pattern e, and the conductor pattern e on which the semiconductor laser 11 is mounted is thermally absorbed by the Peltier element stand 12.
The semiconductor laser 11 and the metal case 13 are connected to the metal case 13 through the capacitive element 21 and the inductive element 25, which have large thermal resistance, so that a sufficient temperature difference between the semiconductor laser 11 and the metal case 13 can be ensured.

In the above embodiment, the second conductor pattern e is connected to the substrate 20.
Although it is formed so as to be folded back at the end surface, this can be similarly implemented by connecting the patterns on the upper and lower surfaces with through holes. Further, although the second conductor pattern e is connected through the inductive element 25, it may be temporarily taken out of the metal case 13 through a lead and connected to a constant potential point. In this case, the conductor pattern e
The thermal resistance between the metal case 13 and the metal case 13 increases, and the thermal characteristics can be further improved.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a semiconductor laser device that is thermally stable and can dramatically improve the modulation speed.

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional view showing the structure of an embodiment of a semiconductor laser device according to the present invention, and FIG. 2 is a partial cross-sectional view showing the structure of a conventional semiconductor laser device. 11... Semiconductor laser, 12... Peltier element stand,
13... Metal case, 14... Signal input lead, 15... Insulating element, 16... Optical fiber 17° 18... Bonding wire, 19... Coaxial connector, b... Coaxial, C... Support stand, 20... Board,
d, e, f...Conductor pattern, 21...Capacitive element, 22...Laser drive device, 23.24...Bonding wire, 25...Inductive element wire.

Claims (1)

[Scope of Claims] A semiconductor laser having electrodes on surfaces facing each other; a substrate on which a conductive pattern is formed on the front and back surfaces, and on which the semiconductor laser is placed and fixed; one end of this substrate is placed and fixed. a Peltier device stand for storing the semiconductor laser, the substrate, and the Peltier device stand;
a metal case formed with a beam having the same height as the Peltier element stand and on which the other end of the substrate is placed and fixed; a coaxial connector in which a coaxial to which a coaxial line, which is a modulation signal transmission line of a cable, is connected is protruded inside, and a periphery to which a shielded wire, which is a reference potential line of the coaxial cable, is connected is electrically connected to a metal case; an optical fiber cable that is attached to the metal case and has a tip of the optical fiber line located at a laser beam emission position of the semiconductor laser, and the conductive pattern formed on the substrate includes at least a first It consists of a first conductor pattern, a second conductor pattern connected to the front and back surfaces, and a third conductor pattern formed on the front surface, and the first conductor pattern is in contact with the beam and electrically conductive. formed to be connected to
The second conductor pattern is formed to be in contact with the Peltier element base and to be electrically connected to one electrode of the semiconductor laser, and the third conductor pattern is formed to be in contact with the Peltier element base and to be electrically connected to one electrode of the semiconductor laser. the first and second conductor patterns are coupled to each other by a capacitive element, the second conductor pattern is connected to the metal case via an inductive element, and the third conductor pattern is connected to the metal case through an inductive element. is directly or indirectly connected to the other electrode of the coaxial and semiconductor laser.