JPH0814895B2 - Optical information processing device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical pickup used for writing, erasing, and reading signals on an optical recording medium such as an optical disk, or an optical sensor for measurement using light. The present invention relates to an optical information processing apparatus such as the above, and is particularly intended to realize a compact and lightweight optical system.

2. Description of the Related Art In recent years, the demand for optical information processing has increased, and higher performance and lower prices have been demanded.

In particular, for an optical pickup for writing and reading information on an optical recording medium, an integrated optical pickup has been proposed in order to realize speeding up and downsizing.

The outline of the proposed optical pickup is shown in FIG.

The light emitted from the semiconductor laser 21 propagates through the dielectric waveguide 23 formed on the Si substrate 22, and is focused on the surface of the optical disc 25 by the focusing grating coupler 24. The light reflected by the optical disk 25 is converted into guided light by the focusing grating coupler 24 again and returns to the direction of the semiconductor laser 21. However, in part,
The beam is split into two directions by the focusing beam splitter 26 and is input to a pair of light receiving elements, and the reproduction of the recording signal, the focusing, and the tracking signal are detected.

However, the biggest drawback of this method is that the light reflected on the surface of the optical irradiation medium such as an optical disk is returned to the semiconductor laser 21, and as a result, the output of the semiconductor laser fluctuates, In addition, since the oscillation spectrum changes, the focusing property of the focusing grating coupler with large wavelength dispersion deteriorates.

As described above, the present invention reduces the influence of the reflected light from the light irradiation medium on the semiconductor laser and realizes a high quality and high performance thin film optical information processing apparatus.

Means for Solving the Problems The present invention provides a semiconductor laser and linearly polarized light emitted from the semiconductor laser, which is TE or TE corresponding to the polarization plane.
An optical waveguide layer propagating as any one of the TM modes and the specific mode propagating in the optical waveguide layer are coupled, and the propagating light of the specific mode is radiated to a space outside the optical waveguide layer as linearly polarized light. A first grating coupler, a phase plate for converting the linearly polarized light radiated from the first grating coupler into the space outside the optical waveguide layer into elliptically polarized light or circularly polarized light, and the first grating coupler A second light beam is arranged near the semiconductor laser and a part of the light from the phase plate is coupled to propagation modes orthogonal to the specific mode.
And a light receiving element that is formed on the substrate on which the optical waveguide is formed and detects the light coupled by the second grating coupler, the optical waveguide, the first grating coupler, and The optical information processing device is one in which the second grating coupler and the light receiving element are integrated on the same substrate.

According to the present invention, TE or TM mode light propagating through an optical waveguide is emitted as linearly polarized light by a grating coupler, and when the light is passed through a phase plate, it is converted into circularly polarized light or elliptically polarized light, and then, in an optical disc. When reflected and passed through the phase plate again, the polarization axis is almost 90 °.
This applies to the fact that the rotated linearly polarized light is not coupled with the propagation mode in the optical waveguide by the grating coupler, and as a result, does not affect the semiconductor laser as returned light.

Embodiment An embodiment of the present invention is shown in FIG. The emitted light from the semiconductor laser 32 that emits linearly polarized light parallel to the surface of the Si substrate 31,
The first waveguide formed of the SiN layer propagates in the TE mode through the optical waveguide formed of the SiO ₂ layer 33 and the glass layer 34 formed on the surface of the substrate.
It is radiated by the focusing grating coupler 35 and is focused on one surface of the optical disc 37 through the λ / 4 phase plate 36. The light reflected on the disk surface returns along the almost same path as when it was incident, and while it spreads slightly due to the diffraction phenomenon of the light, it is converted by the phase plate 36 into linearly polarized light with a 90 ° polarization direction. It is incident on the first focusing coupler and the second grating coupler. However, this linearly polarized light is TM of the waveguide propagation light.
Although the mode is excited, since the effective refractive index of the waveguide is different between the TE mode and the TM mode, the light returning from exactly the same direction as the direction in which the TE mode is coupled and emitted. Since the TM mode is not coupled, the light reaching the first focusing grating coupler does not return to the semiconductor laser.

The second grating coupler 38 is designed so that the reflected light from the optical disc rotated by 90 ° in the polarization direction and the TM mode of the waveguide are combined and the light is condensed in the vicinity of the two pairs of light receiving elements 39. There is. The second grating coupler diffracts a part of the incident laser light, but does not condense it on a specific point, so that it does not affect the condensing characteristic on the optical disc or the light detecting characteristic. .

In the above embodiment, the case where the guided light is condensed on the recording medium by the condensing grating coupler is shown.
Obviously, it is also applied to the case of condensing light through the lens system.

EFFECTS OF THE INVENTION As described above using the embodiments, according to the present invention,
It is possible to realize a high-performance thin-film optical information processing device that is not affected by the return light from a medium such as an optical disk.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of an optical information processing apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic perspective view of a conventional apparatus. 1 ... Si substrate, 2 ... semiconductor laser, 4 ... glass layer,
5 ... Grating coupler, 6 ... Phase plate, 7 ... Optical disk, 9 ... Light receiving element.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical indication H01S 3/18

Claims (1)

[Claims] 1. A semiconductor laser, an optical waveguide layer that propagates linearly polarized light emitted from the semiconductor laser as a specific mode of either TE or TM mode corresponding to the polarization plane, and propagates through the optical waveguide layer. A first grating coupler that is coupled to the specific mode to radiate propagating light of the specific mode as linearly polarized light to a space outside the optical waveguide layer; and from the first grating coupler to outside the optical waveguide layer. A phase plate for converting the linearly polarized light radiated into space into elliptically polarized light or circularly polarized light, and a part of the light from the phase plate, which is arranged in the vicinity of the semiconductor laser side of the first grating coupler, A second grating coupler that couples with the propagation mode orthogonal to the specific mode, and a second grating coupler formed on the substrate on which the optical waveguide is formed. The second
A light receiving element for detecting light coupled by the grating coupler, the optical waveguide, the first grating coupler, the second grating coupler, and the light receiving element are integrated on the same substrate. Processing equipment.