JPH0138288B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a coupling device on the input side of an optical isolator.

Configuration of conventional example and its problems As shown in FIG. Since the end face is a plane perpendicular to the optical axis, the reflected light from the rod lens end face returns to the semiconductor laser 1 before entering the isolator body 3, which causes adverse effects such as fluctuations in the emission wavelength of the semiconductor laser 1. There was a problem that the coupling efficiency deteriorated.

OBJECT OF THE INVENTION An object of the present invention is to provide a coupling device on the incident side of an optical isolator that can reduce reflected light from an optical system and increase coupling efficiency.

Structure of the Invention The present invention utilizes the fact that the light emitted from a semiconductor laser spreads in the horizontal and vertical directions, and that the light emitted from the semiconductor laser is polarized, and uses two cylindrical lenses. The frontmost generatrix or cylinder axis of the cylindrical surface of the cylindrical lens No. 1 is located within the polarization plane of the laser beam, and the cylinder axis is tilted at the Brewster angle to eliminate reflection from the cylindrical surface to the semiconductor laser, Further, a second cylindrical lens having a cylindrical axis perpendicular to the first cylindrical lens converts the emitted light from the semiconductor laser into parallel light together with the first cylindrical lens, and the first cylindrical lens is aligned with the optical axis. In order to correct the deviation of the optical path from the optical axis due to the tilting of the second cylindrical lens, the flat side of the second cylindrical lens is directed toward the first cylindrical lens, and the flat side faces the same angle and opposite direction as the first cylindrical lens. The optical path is made to coincide with the optical axis by tilting the lens. In this way, reflected light can be reduced and the coupling efficiency between the isolator body and the semiconductor laser can be increased.

DESCRIPTION OF THE EMBODIMENTS An embodiment of the present invention is shown in FIGS. 2 to 5. That is, since the semiconductor laser has a spread angle of about 20 degrees and about 5 in the horizontal and vertical directions, in order to make this into parallel light, there is a space between the semiconductor laser 4 and the isolator main body 7, in which their cylindrical axes are perpendicular to each other. cylindrical lenses 5 and 6 are arranged. Furthermore, since the semiconductor laser 4 is almost 100% polarized, the semiconductor laser 4 is set so that the plane of polarization lies on the XZ plane in FIG. The cylindrical axis of the first cylindrical lens 5 lies within the XZ plane and is inclined at a predetermined angle with respect to the There is no reflected light. Since the light that enters the cylindrical surface (curved surface) that is the front surface of the first cylindrical lens 5 has a spread angle, the cylindrical lens 5 reflects all light at a slight deviation from the Brewster angle. However, since the frontmost surface of incidence is a cylindrical surface, the reflected light does not return to the semiconductor laser. Next, the first cylindrical lens 5
Because the lens is tilted, the light traveling inside the first cylindrical lens 5 travels deviated from the optical axis P as shown in FIG.
Therefore, the plane 6a side of the second cylindrical lens 6 is
A plane 6a is tilted by the same angle in a direction opposite to the first cylindrical lens 5 with respect to the X-axis in a plane that faces the first cylindrical lens 5 and includes the optical axis. In addition, the second
The output side of the cylindrical lens 6 has a curved surface as shown in FIG. 3, so that the output light can be changed into parallel light. In this case, the second cylindrical lens 6
Since the cylindrical axis of coincides with the Y axis, light spreading in the X direction can be converted into parallel light. In this way, the first cylindrical lens 5 and the second cylindrical lens 6 are tilted in opposite directions with respect to the X axis by the Brewster angle, so that the first cylindrical lens 5 and the second cylindrical lens 6 Reflection on each cylindrical surface and flat surface can be reduced, and at the same time, the optical axis can be aligned between the front and rear of the two lenses (the light in front of the first cylindrical lens 5 and the light after passing through the second cylindrical lens 6). The axes can be aligned.

As mentioned above, this isolator coupling device
The emitted light is converted into parallel light by two cylindrical surfaces perpendicular to each other, reflection from the lens is eliminated by tilting the cylindrical lens at the Brewster angle, and optical path deviation is eliminated by tilting the two cylindrical lenses in opposite directions. It has a high practical value because the influence can be eliminated and the coupling efficiency with the optical isolator main body 7 can be increased.

ADVANTAGEOUS EFFECTS OF THE INVENTION The coupling device on the incident side of an optical isolator of the present invention has the advantage of suppressing reflected light and increasing the coupling effect between the semiconductor laser and the isolator body.

[Brief explanation of drawings]

Fig. 1 is a schematic side view of a conventional example, Fig. 2 is a schematic side view of an embodiment of the present invention, Fig. 3 is an enlarged view thereof, Fig. 4 is a bottom view of Fig. 2, and Fig. 5 is a schematic side view of an embodiment of the present invention. FIG. 2 is a perspective view of FIG. 2; 4... Semiconductor laser, 5... First cylindrical lens, 6
...second cylindrical lens, 7...isolator body.

Claims (1)

[Claims] 1. A semiconductor laser, which is placed on the emission side of the semiconductor laser, and whose cylindrical axis is located within the polarization plane of the laser beam, and whose curved side is tilted at the Brewster angle with respect to the optical axis of the laser beam. a first cylindrical lens that is disposed on the transmission side of the first cylindrical lens so that its cylindrical axis is perpendicular to the plane that includes the cylindrical axis of the first cylindrical lens and the optical axis; a second cylindrical lens whose flat side faces the first cylindrical lens, whose flat side is rotated around the cylindrical axis and tilted in the opposite direction at the same angle as the first cylindrical lens, and whose output side is curved; , and an optical isolator body disposed on the transmission side of the second cylindrical lens.