JPH04113327A - Laser beam source - Google Patents

Abstract

PURPOSE:To vary the polarized states, quantities, etc., of respective projection beams, one by one, or set them independently by providing a single-mode channel type optical waveguide, a laser beam emitting means, a TE-TM mode converter, and a TE-TM mode splitter. CONSTITUTION:Light emitted by a laser diode 1 is made incident on an optical waveguide 3. If the incident light is in, for example, TE mode in this case, this light has its plane of polarization rotated by a desired quantity through the operation of the mode converter 4 and is converted into a TE-mode component and a TM-mode component at an optional ratio; and the light which has those mode components is made incident on the mode splitter 5, which outputs the light of the TE mode and the light of the TM mode to optical waveguides 6 and 7 respectively, so that they are emitted from outgoing terminals 8 and 9. The outgoing terminals 8 and 9 can be regarded as laser beam sources. Namely, the single laser diode can be used substantially as LD arrays for two beams, whose polarized states, light quantities, etc., can be made different from each other, so that light beams in mutually orthogonal polarized states can be outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a laser light source, and relates to a multi-beam laser light source that is used, for example, in an optical disk head and can change the polarization state of each beam.

[Prior Art] In a rewritable optical disk device, RAW (Read
Demand for multi-beam LD (laser diode) arrays is increasing for various purposes such as after-write checking, parallel transfer, and other purposes.

A multi-beam LD array has a plurality of laser diodes formed on a common semiconductor substrate, and can constitute a multi-beam laser light source with a single chip.

[Problems to be Solved by the Invention] However, due to the structure of a multi-beam LD array, it is not possible to change the polarization state for each beam. Therefore, all the emitted beams have the same polarization plane, and due to the structure of the optical system, it is not possible to change the polarization state for each beam. There are big restrictions. Furthermore, it is difficult to produce a multi-beam LD array of uniform quality, and there is also the disadvantage that the cost of the device increases.

An object of the present invention is to make it possible to realize a multi-beam laser light source without using a multi-beam LD array, which is difficult to fabricate, in view of the problems in the conventional apparatus described above.

An object of the present invention is to provide a laser light source in which the polarization state, light intensity, etc. of each emitted beam can be made different for each beam, or can be set independently for each beam.

[Means for Solving the Problems] A laser light source according to the present invention includes a single mode channel type optical waveguide formed on a waveguide substrate, and a laser light emitting means whose output end is optically coupled to one end of the optical waveguide. and,
It is characterized by comprising a TE-TM mode converter formed in the optical waveguide, and a TE-TM mode splitter formed in the waveguide substrate and coupled to the output of the TE-TM mode converter.

Further, the output of the TE-TM mode splitter is connected to two single mode channel type optical waveguides for respectively transmitting TE and TM acid components, and each optical waveguide is configured to be provided with an optical switching device using an electro-optic effect. I can bring it.

Further, the laser emitting means may be a semiconductor laser integrally formed with the waveguide substrate.

[Operation] In the above configuration, the light emitted from the laser emitting means enters the single mode channel type optical waveguide formed on the waveguide substrate, and the plane of polarization is rotated by a desired amount by the TE-TM mode converter. Then, the output of the TE-TM mode converter is separated into a TE mode component and a TM mode component by a TE-TM mode splitter and output as a multi-beam light source. In this case, the TE and TM mode components can be generated at any ratio by adjusting the amount of rotation of the polarization plane in the TE-TM mode converter. That is, a multi-beam laser light source array in which each beam has a different polarization state is realized. Therefore, the original laser diode is LD
In addition to arrays, single laser diodes may also be used. That is, according to the basic configuration of the present invention, two beams of light having different polarization directions can be emitted from a single laser diode.

However, if a single mode channel optical waveguide is connected to each output of the TE-TM mode splitter, and an optical switching device using the electro-optic effect is provided in each optical waveguide, the voltage applied to the switching device will be By controlling it, the light intensity of the emitted beam can be adjusted independently to an arbitrary value.

Furthermore, by using a compound semiconductor such as GaAs or InP for the waveguide substrate and forming the laser emitting means monolithically on the waveguide substrate, a highly reliable multi-beam laser light source with a simple structure is realized. can do.

[Example] Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows a multi-beam laser light source according to a first embodiment of the invention. In the laser light source shown in the figure, a single mode channel type optical waveguide 3 formed on a substrate 2 such as lithium niobate (LiNbO3) having an electro-optic effect is connected to a laser diode 1, and a single mode channel type optical waveguide 3 is formed on a substrate 2 such as lithium niobate (LiNbO3) that has an electro-optic effect. The optical waveguide 3 and the optical waveguide 3 are bonded to each other so that the coupling efficiency between the optical waveguide 3 and the optical waveguide 3 is maximized. Moreover, the optical waveguide 3 is TE-TM
The mode converter 4 is usually constructed by loading a comb-shaped electrode or a flat plate electrode on an optical waveguide, and the main axis of the index ellipsoid of the substrate is rotated by an applied electric field. This is a well-known device that uses

The leading wavepath emerging from the mode converter 4 is then coupled to a moto splitter 5. As the mode splitter 5, various known types can be used, including, for example, a tuple mode type mode splitter in which a double mode region is provided in a certain section and the complete coupling lengths of the TE mode and the TM mode are different. Furthermore, single mode optical waveguides 6 and 7 are connected to the output of mode splitter 5, respectively, and the terminal ends of these optical waveguides 6 and 7 constitute output ends 8 and 9, respectively.

In such a configuration, the light emitted from the laser diode 1 enters the optical waveguide 3. If the incident light in this case is, for example, TE mode, the plane of polarization of this light is changed by the action of the mode converter 4. It is rotated by a desired amount and converted into TE mode components and TM mode components of arbitrary ratios.

The light having these TE and TM mode components then enters the mode splitter 5, and the TE mode light and the TM mode light are outputted to the respective optical waveguides 6 and 7, and are emitted from the output ends 8 and 9, respectively. Ru. Therefore, each output end 8 and 9 can be considered as a laser light source.

In FIG. 1, the light emitted from each output end 8 and 9 has a polarization state perpendicular to each other, but by newly providing a mode converter on each single mode optical waveguide 6 and 7, both output ends 8 and 9 It is also possible to independently set one polarization state of the light emitted from the light source and the light source 9 to any desired state.

FIG. 2 shows a laser light source according to a second embodiment of the invention. The laser light source shown in FIG. 2 is a laser light source in which the amount of light emitted from the emission ends 8 and 9 of the laser light source shown in FIG. 1 can be independently controlled. That is, the second
In the figure, a laser diode 1, a single mode channel type optical waveguide 1% 3, a TE-TM mode converter 4,
The configuration up to mode splitter 5 is the same as that in FIG. However, in the laser light source of Fig. 2,
Optical switching devices 10 and 11 are coupled to each single mode optical waveguide 6 and 7 branched from mode splitter 5, respectively. As an example of these optical switching devices, TE (or T
M) An active mode splitter that can arbitrarily change the mode splitting ratio is shown. These active mode splitters 0 and 11 are each equipped with a tuple mode waveguide and electrodes shown with diagonal lines, and the splitting ratio of the amount of output light can be arbitrarily controlled by controlling the voltage applied between each electrode. Of the output ends 12 and 13 connected to the two branched outputs of the active mode splitter 10, the output end 13 is provided with an absorbing material shown by diagonal lines. Furthermore, of the output ends 14 and 15 connected to the output of the active mode splitter 1, the output end 15 is also provided with an absorbing material shown by diagonal lines.

In the laser light source of FIG. 2, the light emitted from the laser diode 1 passes through a mode converter 4 and a mode splitter 5 to each optical waveguide 6 and 7, as in the case of FIG. mode light, and each optical switching device 10 and 11
incident on . These optical switching devices 10 and 1
Desired voltages (1) and (2) are respectively applied between the electrodes 1 to control the branching ratio of the incident light to a desired value. Therefore, the amount of light emitted from the output ends 12 and 14 is determined by each voltage
and (2) can be controlled to a desired value. Output ends 13 from each optical switching device 10 and 11 respectively.
and 15 are absorbed and removed by the absorbing material, respectively.

Note that instead of providing absorbers at the output ends 13 and 15,
It is also possible to remove it by utilizing reflection or scattering off the axis of the waveguide. In addition, each optical switching device 10
The voltages Vl and v2 applied to the electrodes 11 and 11 are limited to DC voltages, for example pulse voltages, so that the emission timing and other aspects of the light output from each emission @12 and 14 can be arbitrarily controlled.

[Effects of the Invention] As described above, according to the present invention, for example, a single laser diode can be used substantially as a two-beam LD array, and the polarization state and light intensity of both beams can be adjusted to each other. It becomes possible to make them different. Therefore, it is also possible to output light with mutually orthogonal polarization states, which is difficult to achieve especially with a multi-beam LD array. It is also possible to place the output ends of each light beam very close to each other.

Further, according to the present invention, it is possible to change the amount of emitted light or switch the emitted light without changing the output of the laser diode itself or blinking, thereby extending the life of the laser diode and reducing the output light. Wavelength stabilization can be achieved.

Further, since the laser diode does not need to be used at low power, noise caused by the low power state can be avoided.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing the structure of a laser light source according to one embodiment of the present invention, and FIG. 2 is an explanatory diagram schematically showing the structure of a laser light source according to another embodiment of the present invention. be. 1: Laser light source, 2: Substrate, 3 Single mode channel optical waveguide, 4: Mode converter, 5: Mode splitter, 6.7: Single mode optical waveguide, 8.9.12.13.14, 15: Output End, 10.11
: Optical switching device, Vl, V2: Control power supply.

Claims (1)

[Claims] 1. A single mode channel type optical waveguide formed on a waveguide substrate; a laser emitting means having an output end optically coupled to one end of the optical waveguide; and a laser emitting means formed in the optical waveguide. A laser light source comprising: a TE-TM mode converter; and a TE-TM mode splitter formed on the waveguide substrate and coupled to an output of the TE-TM mode converter. 2. The output of the TE-TM mode splitter is connected to two single-mode channel type optical waveguides that respectively transmit the TE and TM components, and each optical waveguide is provided with an optical switching device using an electro-optic effect. The laser light source according to item 1. 3. The laser light source according to claim 1 or 2, wherein the laser emitting means is a semiconductor laser monolithically formed on the waveguide substrate.