JP2970703B2 - Semiconductor laser module - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser module having a built-in signal line for driving a semiconductor laser and a bias circuit, and more particularly to a semiconductor laser module used as a light source for a high-speed optical communication system.

[0002]

2. Description of the Related Art FIG. 4 is a sectional side view of a conventional semiconductor laser module.

Referring to FIG. 4, a semiconductor laser 1, a laser light monitoring photodiode 4, a lens 3 for coupling to an optical fiber 6, and a laser temperature monitoring thermistor 2
Are mounted on the carrier 5.

A ceramic substrate 9 for fixing the chip inductor 8 by soldering is fixed to the carrier 5 by brazing.

[0005] The carrier holding block 10 has a low thermal conductivity,
In addition, a metal plate is brazed to one end surface (upper surface) of a material having a high dielectric constant, the other end surface (lower surface) is metallized, and the other end surface (lower surface) is brazed to the bottom surface of the hermetic package 7 to form an integral structure. It has become. The bottom surface of the laser-mounted carrier 5 is one end surface (upper surface) of the carrier holding block 10.
And fixed by welding with a YAG laser (yttrium aluminum garnet laser).

The electronic cooler 13 composed of a Peltier element is
A low melting point solder B15 (for example, a melting point of 143 ° C.) is applied to the bottom surface of the electronic cooler 13, the solder is melted, and then cooled to be fixed to the metalized airtight package 7. The carrier 5 is metallized, and is fixed to the upper surface of the electronic cooler 13 by applying a low melting point solder A14 (for example, melting point of 117 ° C.) to the upper surface of the electronic cooler 13, melting the solder, and then cooling. Have been.

Each terminal of the photodiode 4 for monitoring laser light and the thermistor 2 for monitoring laser temperature mounted on the carrier 5 is connected to each line of the hermetic package 7 as shown in FIG.
Are connected as shown in FIG.

In a semiconductor laser module requiring high speed and high optical output, a configuration is used in which a signal line and a bias line are provided separately, and a resistor for impedance matching with a drive circuit is arranged in the signal line. In the semiconductor laser module of FIG. 5, as a signal system line for driving the semiconductor laser 1, the semiconductor laser is connected to a microstrip line A17 designed for a 50Ω system by a bonding wire A16. The microstrip line A17 (50Ω system) is connected to the microstrip line B19 (50Ω system) via the impedance matching thin film resistor 18.

As shown in FIG. 6, a ceramic block 27 is provided on the side surface of the hermetic package 7, and a lead terminal 28 is fixed to the upper surface of the ceramic block 27 by soldering, and the lower surface is used to form a microstrip line. Fully metallized. The microstrip line B19 is connected to the bonding wire B20 by 50.
Line A2 designed for Ω-based microstrip line
5 is connected.

As a bias circuit for driving the semiconductor laser 1, a microstrip line A17 connected to the semiconductor laser 1 by a bonding wire A16 is connected to an inductor pad A22 by a bonding wire C21. Then, it is connected to the inductor pad B23 via the chip inductor 8.
B23 for inductor pad is bonding wire D
24, a line B2 connected to the lead terminal 28 by
6 is connected.

[0011]

FIG. 7 shows an electrical equivalent circuit of a conventional semiconductor laser module (FIG. 4) including an airtight package.

In FIG. 7, the dashed line indicates the equivalent circuit of the semiconductor laser, the dashed line indicates the equivalent circuit of the inductor, the dashed line indicates the equivalent circuit of line B, and the dashed line indicates the equivalent circuit. Represents a bias circuit.

As described above, the anode of the semiconductor laser 1 is a parallel circuit of the parasitic inductance L _w2 of the bonding wire, the parasitic capacitance _{Ch 1} of the carrier holding block + the resistance R _h1 , and the impedance Z _p of the electronic cooler 13. Are electrically grounded.

The cathode of one of the semiconductor lasers is 50
It is connected to the microstrip line MSL1 designed for the Ω system by the inductance L _{w1 of the} bonding wire. The microstrip line MSL2 are connected to the microstrip line MSL3 through an impedance matching thin film resistor R _1, further by a bonding wire inductance L _w4 is connected to MSL3 (line A), the signal source SIG (R _s = 50Ω ).

[0015] Then, as a bias circuit, microstrip line MSL1 is connected to the inductor, represented by a bonding wire inductance L _w4 an equivalent circuit in the two-dot chain line. Then, it is connected to a line B represented by an equivalent circuit composed of the inductance L _s and the parasitic capacitance C _s1 indicated by the three-dot chain line by the inductance L _{w5 of the} bonding wire. The two pads for the inductor are represented by parasitic capacitances C _p1 and C _p2 .

In FIG. 4, the length of the line B is 4 mm, the width is 1 mm, the thickness of the ceramic block is 1 mm, and the relative permittivity is 9.
When L is 6, L _s = 1.7 nH and C _s1 = 0.7 pF.

The conventional semiconductor laser module has a problem that the small signal frequency characteristic is deteriorated as shown in FIG. 8 due to the parasitic capacitances C _p1 , C _p2 , C _b , and C _s1 in the bias circuit.

An object of the present invention is to provide a configuration of a semiconductor laser module capable of greatly improving the band limitation of small signal frequency characteristics.

[0019]

SUMMARY OF THE INVENTION The present invention provides a semiconductor laser, an optical fiber, coupling means for coupling light emitted from the semiconductor laser to the optical fiber, and wiring for connection to an external circuit. In a semiconductor laser module having an airtight package having a dielectric block provided with a pattern on an upper surface, and at least the semiconductor laser and a bias circuit for driving a semiconductor laser built in the airtight package, at least the bias circuit of the dielectric block is provided. And a metal film formed on the lower surface of the dielectric block corresponding to the wiring pattern connected to the dielectric block is removed.

[0020]

Next, a semiconductor laser module according to the present invention will be described with reference to the drawings.

FIG. 1 is a side sectional view showing one embodiment of the semiconductor laser module of the present invention. The description of the same components as those in the conventional example is omitted.

A lead terminal 28 for connection to an external circuit is brazed and fixed to the ceramic block 27 in the hermetic package 7, and metallization on the lower surface of the bias line including the lead terminal 28 is removed.

FIG. 2 shows an electrical equivalent circuit of the semiconductor laser module (FIG. 1) of the present embodiment including the entire hermetic package.

In FIG. 2, the dashed line indicates the equivalent circuit of the semiconductor laser, the dashed line indicates the inductor equivalent circuit, the dashed line indicates the bias circuit, and the dashed line indicates the line. The equivalent circuit of B and the broken line represent the bias circuit.

[0025] as a bias circuit for driving the semiconductor laser 1, a microstrip line MSL1 is connected to the inductor, represented by a bonding wire inductance L _w4 an equivalent circuit in the two-dot chain line. Then, it is connected to the line B represented by an equivalent circuit in the three-dot chain line by the inductance _{Lw5 of the} bonding wire.

At this time, the parasitic capacitance of the line B in the equivalent circuit disappears.

By removing the metallization on the lower surface of the bias line disposed in the ceramic block in the hermetic package, the parasitic capacitance in the bias circuit can be reduced. As shown in FIG. As a frequency band of 2.9 GHz, the frequency band of the conventional semiconductor laser module shown in FIG.
Can be greatly improved.

[0028]

As described above, in the semiconductor laser module of the present invention, since the metallization on the lower surface of the bias line disposed in the ceramic block in the hermetic package is removed, the parasitic capacitance in the bias circuit can be removed, and the modulation characteristics can be reduced. Has the effect of greatly improving

[Brief description of the drawings]

FIG. 1 is a side sectional view showing one embodiment of a semiconductor laser module of the present invention.

FIG. 2 is a diagram showing an equivalent circuit of the semiconductor laser module shown in FIG.

FIG. 3 is a diagram showing an example of a small signal frequency characteristic in the semiconductor laser module of the present invention.

FIG. 4 is a view showing a conventional semiconductor laser module.

5 is a diagram showing internal connections of the semiconductor laser module shown in FIG.

FIG. 6 is a side sectional view of the semiconductor laser module shown in FIG. 4;

FIG. 7 is a diagram showing an equivalent circuit of the semiconductor laser module shown in FIG.

FIG. 8 is a diagram showing an example of a small signal frequency characteristic in a conventional semiconductor laser module.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 semiconductor laser 2 thermistor 3 lens 4 monitor photodiode 5 laser carrier 6 optical fiber 7 airtight package 8 inductor 9 ceramic substrate 10 carrier holding block 11 substrate fixing block 12 cavity 13 electronic cooler 14 low melting point solder A 15 low melting point Solder B 16 Bonding wire A 17 Microstrip line A 18 Thin film resistor for impedance matching 19 Microstrip line B 20 Bonding wire C 21 Bonding wire C 22 Inductor pad A 23 Inductor pad B 24 Bonding wire D 25 Line A 26 Line B 27 ceramic block 28 lead terminal 29 metallized part 30 metallized removing part

Claims (2)

(57) [Claims] 1. A dielectric block having a semiconductor laser, an optical fiber, coupling means for coupling light emitted from the semiconductor laser to the optical fiber, and a wiring pattern for connection to an external circuit provided on an upper surface. A semiconductor laser module having at least the semiconductor laser and a semiconductor laser driving bias circuit built in the airtight package, wherein a lower surface of the dielectric block corresponds to a wiring pattern of the dielectric block. Wherein the metal film formed on the semiconductor laser module is removed. 2. The semiconductor laser module according to claim 1, wherein said metal film is removed corresponding to a wiring pattern connected to said bias circuit on said dielectric block. module.