JPS6120389A - Laser module - Google Patents

Abstract

PURPOSE:To maximize the coupling efficiency of the coupling system by obtaining magnifications by a factor of three time or more even when the distance between a semiconductor laser and a rod lens is set at 1.0mm. or more, by a method wherein a convergent rod lens of short pitch of less than a specific value is used in a laser module in which the light from a semiconductor laser is collected by means of a convergent lens and made to come into an optical fiber. CONSTITUTION:The light emitting out of the semiconductor laser LD4 is collected by means of a SELFOC micro lens SML5 and then coupled to the optical filter 6. It is necessary to set the coupling system at optimum magnifications in accordance with the kind of LD4 and optical fiber 6 in order to maximize the coupling efficiency. Optimum magnifications can be obtained in setting the distance l1 at 1.0mm. or more by reducing the pitch of the SML5 to 0.19. Since an LD4 with a protection cap yields a 0.7mm. distance from the LD5 to the surface of cap glass, the distance l1 should be set at 0.7mm. or more. Although the conventional SML of 0.25 pitch have yield the magnification only by a factor of three times, setting the SML5 at a pitch of less than 0.25, particularly 0.19, enables high magnifications over a wide range even when l1 is increased to 1.0mm. or more.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF THE INVENTION The present invention relates to a laser module that focuses light from a semiconductor laser using a focusing rod lens and inputs the light into an optical fiber.

1. Structure of a conventional example and its problems FIG. 1 shows a laser module using a conventional 025 pitch SELFOC microlens. In FIG. 1, 1 is a semiconductor laser LD, 2 is a SELFOC microlens SML, 3TL, and a fiber. Further, 11 is the distance between the LDI and the SML 2, and 12 is the distance from the output end face of the SML 2 to the condensing point. l! If l is set to l, Qii, 1!2 becomes 45 friends and the magnification becomes 21 times,
If you set 11 to 0.5 ho! ! 2 is 9. Q mm, and the magnification is 42 times.

In order to obtain a high coupling efficiency between the LDI and the optical fiber 3, a magnification of 3 to 10 times is required in the case of a GI fiber, and 4 times to 7 times in the case of a single mode fiber.

In a conventional laser module using 0.25 pitch SML2, 11 must be 0.7 to obtain a high magnification of 3 times or more.
It must be set below u, but from L D 1 to L
D Because the distance to the glass surface of the protective cap is 07mm, l! 1 cannot be set to Q, 7 mar or less, and the coupling efficiency between the LDI and the optical fiber 3 cannot be made high.

Purpose of the Invention The present invention eliminates the problems of the above-mentioned conventional example,
Set el to 1. The purpose is to obtain a magnification of 3 times or more even when set to Qii or more, and to maximize the coupling efficiency of the coupling system.

Structure of the Invention In order to achieve the above object, the present invention uses a converging rod lens with a pitch shorter than 0.23 pitch, so that even when /1 is set to l, Q 1111 or more, the This makes it possible to obtain a magnification of This provides the effect of achieving maximum coupling efficiency.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In Fig. 2, 4 is a semiconductor laser LD, 5 is a SELFOC microlens SML with a pitch of 0.19, and 6
is an optical fiber. The light exiting the LD 4 is collected by the SML 5 and coupled to the optical fiber 6 .

l with the pitch of S M L 5 as a parameter! The relationship between 1 and magnification is shown in Figure 3. In the case of 0.19 pitch compared to the case of 025 pitch! Even if + is large, a high magnification can be obtained. Theoretical coupling efficiency curves between the LD 4 and the optical fiber 6 are shown in FIGS. 4 and 5.

In order to maximize the coupling efficiency, it is necessary to set the coupling system to an optimal magnification depending on the type of LD 4 and optical fiber 6. By setting the pitch of SML5 to 019, the optimum magnification can be obtained when l] is set to 10 or more. For D4 with a protective cap, the distance from LD4 to the cap glass surface is 0.711m, so /1 is changed to Q.
, it has to be 7 y or more. In the conventional 025 pitch SML, even if /I was set to 0.7 y, the magnification was only 3 times, but by setting SML5 to 0.19 pitch, If LD4.11 is increased, a wide range of high magnification can be obtained even in the case of LD4.9. There is an advantage that the maximum coupling efficiency can be obtained by setting the optimum magnification according to the 60 types of optical fibers.Advantageous Effects of the Invention As described above, the present invention has the advantage that the distance e1 between the semiconductor laser and the SML is Even if you set it higher than me, you can still get high magnification over a wide range, so l! It is possible to set the optimum magnification even for an LD with a protective cap, in which l cannot be lower than Q, 7 io+, and has the advantage that the coupling efficiency between the LD and the optical fiber can be maximized.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a conventional laser module, Fig. 2 is a schematic diagram of a laser module according to an embodiment of the present invention, and Fig. 3 is a schematic diagram of a laser module according to an embodiment of the present invention. A diagram showing the relationship between I and magnification, FIG. 4 is a characteristic diagram of the coupling system magnification m versus coupling efficiency η using the PPP half-width at half maximum of the semiconductor laser of the laser module as a parameter, and FIG. 5 shows the relationship between the semiconductor laser 17 of the laser module ) is a characteristic diagram of coupling system magnification m versus coupling efficiency η with F'FP half width at half maximum as a parameter. 4...Half-four body v-the, 5...Selfoc micro lens, 6...Optical fiber. Name of agent: Patent attorney Toshio Nakao eNaka 1 Meika 1
figure? Figure 2 Figure 3 (asl

Claims (1)

[Claims] A laser module in which a semiconductor laser, a short pitch focusing rod lens with a pitch of 0.23 or less, and an optical fiber are arranged on the same axis.