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Browse Prior Art Database

Planar Photodiode Technology fir Optical Interconnects

IP.com Disclosure Number: IPCOM000105658D
Original Publication Date: 1993-Aug-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Broom, RF: AUTHOR [+3]

Abstract

The photodiodes, as used in fiber-optic transmission systems, require that the incident light be perpendicular to the sensitive surface. A co-linear arrangement, such as used to couple a laser 1 (Fig. 1A) to the output fiber 2, is inefficient. Alternatives, using a prism 3, a mirror or a bevelled fiber 4 are necessary to redirect the light onto the photodiode 5, as illustrated in Fig. 1B.

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Planar Photodiode Technology fir Optical Interconnects

      The photodiodes, as used in fiber-optic transmission systems,
require that the incident light be perpendicular to the
sensitive surface.  A co-linear arrangement, such as used to
couple a laser 1 (Fig. 1A) to the output fiber 2, is
inefficient.  Alternatives, using a prism 3, a mirror or a
bevelled fiber 4 are necessary to redirect the light onto the
photodiode 5, as illustrated in Fig. 1B.

      We describe a modified photodiode geometry which simplifies the
optical  coupling  to the fiber 6, rendering it similar to the
laser/fiber connection.  The principle, illustrated in Fig. 2A,
employs refraction in combination with a tilted facet 7 to direct
the light from the fiber 6 onto the sensitive area of the photodiode

8.  It is applicable to materials and wavelengths for which the
photodiode substrate is transparent, for example InP at &lambda.  =
1.3-1.5 &mu.m.  The angled facet 7 can be formed in a number
of ways such as by cleaving, anisotropic etching or mechanical
polishing.  The two former are illustrated in Fig. 2.  With all
methods the tilt angle is easily controlled.  A large angle reduces
the illuminated area on the photodiode 8, allowing a shorter
response time or greater sensitivity.  The etched facet of Fig. 2B,
may be combined with alignment grooves 9 for the fiber 6, as
sketched, further  simplifying the structure.  In both cases (Figs.
2A,B) the arrangements are well adapted to...