Optical power limiter

Details Optical power limiter Optical power limiter

1989-08-11

1990-08-28

Sikes, William L.

Radiant energy

Ionic separation or analysis

Static field-type ion path-bending selecting means

350 9610, 350356, 250205, G02B 610

Patent

active

049520164

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to optical power limiters. It finds particular application in optical communications.
A device which has considerable potential for use in optical communications systems is an optical limiter. Placed prior to the photodetector in an optical receiver, it could alleviate problems encountered with dynamic range limitations in conventional receivers.
Different forms of optical limiter have been proposed and demonstrated, a number of which make use of nonlinear optics. If the limiter is formed in an optical waveguide then there are several additional advantages, foremost amongst these being the ability to confine the radiation to small dimensions, ie high power densities, and thus achieve limiting action at relatively modest powers by comparison with bulk (non-waveguide) limiters. Furthermore, if the waveguide is made of a semiconductor material then there exists the potential for integration of the limiter with the photodetector and with other optical components also fabricated as semiconductors.
(An optical waveguide comprises a core region of a first material, and an outer, cladding region of a second material. The refractive index of the core material is higher than that of the cladding material, having the effect of guiding optical radiation transmitted by the waveguide to propagate at least substantially along the core region. Neither the core nor the cladding region necessarily exhibits only one uniform refractive index. In epitaxially grown semiconductor waveguides the core generally has a rectangular cross section, the cladding being provided by characteristics of the layers of the semiconductor structure concerned).
Waveguide optical limiters are known which rely on nonlinear optical behaviour resulting in changes in refractive index with input signal intensity. They rely on the characteristic of certain materials that refractive index increases with optical intensity. Hence they can be designed so that the difference in refractive index of core and cladding materials reduces as input signal intensity increases. As the diffference decreases, the waveguiding properties of the structure decrease until when the refractive index difference disappears altogether, optical radiation is no longer confined even substantially to the core region. If the output of the structure is taken from the core region, this shows a power limited characteristic.
Waveguide optical limiters have been reviewed by Seaton et al (Optical Engineering, Volume 24, No. 4, pp 593-599, 1985). However, because to date most of these have relied on nonlinear optical behaviour wherein refractive index increases with optical intensity, they have relied on nonlinearity of the cladding material of the waveguide, rather than of the core material. That is, as the optical intensity increases, the refractive index of the cladding material (n.sub.s) increases, so reducing the refractive index difference between core and cladding (n.sub.c -n.sub.s) and consequently reducing the strength of the waveguiding characteristic.
Although such a device can act as an optical limiter, its response occurs at relatively high values of input signal intensity for the field of optical communications. This is because the major part of the optical radiation is carried by the core material, not the cladding material, but it is the response of the cladding material which must produce the limiting effect.
Some analyses have been published pertaining to waveguide structures where the nonlinear behaviour occurs in the core (eg Boardman and Egan, IEEE Journal of Quantum Electronics, Vol. QE-22, No. 2, pp 319-324 1986), but because again they rely on materials whose refractive index increase with intensity, the situation considered is that of a self-focussing nonlinearity, ie one where the refractive index of the core material increases with increasing optical intensity, rather than the opposite case of a defocussing nonlinearity. There is therefore no obvious way to make an optical limiter with such a structure.
There is a publication by Ogusu

REFERENCES:
patent: 4093353 (1978-06-01), Lang
patent: 4483004 (1984-11-01), Inaba et al.
patent: 4515429 (1985-05-01), Smith et al.
patent: 4521681 (1985-06-01), Inaba et al.
patent: 4723248 (1988-02-01), Harter et al.
patent: 4765719 (1988-08-01), Fergason
patent: 4775215 (1988-10-01), Teng et al.
patent: 4776677 (1988-10-01), Park et al.
Stryland et al., Two Photon Absorption, Nonlinear Refraction, and Optical Limiting in Semiconductors, pp. 613-623, Optical Engineering, vol. 24, No. 4, Jul./Aug. 1985.
Bogatov et al., Nonlinear Refraction in Semiconductor Lasers (Review), pp. 308-325, Sov. J. Quantum Electron., vol. 15, No. 3, 3/85.
Abashkin et al., Nonlinear Absoption of Light in Glassy Arsenic Sulfide Fibers in the Energy Range Hv<E.sub.g, pp. 1343-1345, Sov. J. Quantum Electron., vol. 12, No. 10, 10/82.
Cada et al, Nonlinear Guided Waves Coupled Nonlinearly in a Planar GaAs/GaAiAs Multiple Quantum Well Structure, pp. 755-757, Appl. Phys. Lett., vol. 49, No. 13, 9/29/86.
Stegeman et al., Nonlinear Integrated Optics, pp. R57-R78, J. Appl. Phys., vol. 58, No. 12, 12/85.
Ogusu, TE Waves in a Symmetric Dielectric Slab Waveguide with a Kerr-Like Nonlinear Permittivity, pp. 65-72, vol. 19, No. 1, Jan. 1987.

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