Thermo-optic semiconductor device

Details Thermo-optic semiconductor device Thermo-optic semiconductor device

1999-07-07

2001-08-21

Chaudhuri, Olik (Department: 2814)

Active solid-state devices (e.g., transistors, solid-state diode

Responsive to non-electrical signal

Electromagnetic or particle radiation

C257S432000, C257S436000, C257S526000, C257S536000, C257S537000, C257S538000, C359S248000, C359S288000, C359S289000, C359S385000

Reexamination Certificate

active

06278168

ABSTRACT:

The invention relates to thermo-optic semiconductor devices having optical characteristics which may be changed by resistive heating.
BACKGROUND OF THE INVENTION
Semiconductors have been used in optical transmission devices. For example, silicon has been used in integrated silicon chip devices. Such devices may include silicon waveguides formed as an integrated circuit on a silicon dioxide layer supported by a silicon substrate. It is known that silicon exhibits a refractive index varying with temperature. It exhibits a refractive thermal non-linearity dn/dT=1.86×10
−4
K
−1
at a wavelength of 1550 nm. This non-linearity with application of heat has been used to form phase modulators in silicon and silica based waveguide devices by using a thin metal track over the waveguide region to provide a resistive heater.
It is an object of the present invention to provide an improved structure and method for effecting resistive heating in a thermo-optic semiconductor device.
SUMMARY OF THE INVENTION
The invention provides a thermo-optic semiconductor device comprising one semiconductor region providing an optical transmission path and an adjacent semiconductor region providing a resistive heater between two doped regions, said doped regions being in electrical contact with external contact regions so that current may be passed through the resistive heater within the adjacent semiconductor region to heat said one semiconductor region and thereby vary its optical characteristics.
Preferably, said external contact regions comprise metal regions.
Preferably, the device is covered with an electrically insulating layer, and said metal regions are exposed through said insulating layer.
The resistive heater may provide a phase shifter for light transmitted through the transmission path.
In some embodiments, the semiconductor device comprises a semiconductor waveguide providing said optical transmission path, and said adjacent semiconductor region extends across the underside of the waveguide.
Preferably, the semiconductor regions are formed of silicon.
The device may be integrated on a silicon or silicon-on-insulator chip.
The doped regions may each comprise P-typed doped regions within the semiconductor.
The doped regions may each comprise N-typed doped regions within the semiconductor.
The present invention includes a light modulator comprising an optical transmission device for splitting an optical beam and directing part of the optical beam through a thermo-optic semiconductor device as aforesaid to cause a phase variation, and means for recombining the beam to cause amplitude modulation by interference.
The present invention includes a method of varying the optical transmission characteristics of a semiconductor device comprising passing current through part of the semiconductor device between two doped regions of the semiconductor device, thereby generating resistive heat to vary the optical transmission characteristics.
Current may be passed between said doped regions to vary the phase of light transmitted through the device.
The power supply may be modulated to modulate the phase variation.
Said semiconductor device may include a semiconductor waveguide adjacent to the region through which current is passed.


REFERENCES:
patent: 2 269 678 (1994-02-01), None
patent: 2 320 104 (1998-06-01), None
International Search Report re PCT application No. PCT/GB99/02016, dated Sep. 13, 1999.
Cocorullo, G. et al, “Silicon Thermooptical Micromodulator with 700-kHz -3-dB Bandwith,”IEEE Photonics Technology Letters, vol. 7, No. 4, pp. 363-365, Apr., 1995.
Cutolo, A. et al, “Silicon Electro-Optic Modulator Based on a Three Terminal Device Integrated in a Low-Loss Single-Mode SOI Waveguide,”Journal of Lightwave Technology, vol. 15, No. 3, pp. 505-518, Mar., 1997.
U.K. Search Report for patent application No. GB 9815655.7 dated Oct. 28, 1998.

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