Wavelength division multiplexing receiver
A demultiplexer-free wavelength division multiplexing receiver based on cascaded-bandgap waveguide photodiodes, includes a substrate; and a plurality of different absorbing material sections forming a plurality of independent photodetector sections, each with a different thickness and a different bandgap. The plurality of photodetector sections may be fabricated at the same time on the same substrate, whereby different widths between each pair of mask stripes results in a different thickness of each photodetector section and a different bandgap of each photodetector section. The photodetector sections are then optically connected together into concatenated photodetector sections forming a single elongated optical waveguide.
1 . A wavelength division multiplexor (WDM) photodetector receiver, comprising:
cascaded-bandgap waveguide photodetector sections with multiple concatenated bandgaps, arranged from lowest wavelength to highest wavelength, based on Multiple Quantum Well (MQW) absorbing media, each photodetector section configured for a corresponding different single wavelength in bandgap and length, wherein the cascaded-bandgap waveguide photodetector sections are aligned and connected into concatenated photodetector sections forming a single elongated optical waveguide adapted for guiding an incoming signal successively through each waveguide photodetector section,
wherein a respective minimum photodetector length is defined for absorbing a respective single wavelength, and
at least one of the photodetector sections is configured longer than a corresponding respective minimum photodetector length for absorbing the respective corresponding different single wavelength.
2 . The WDM photodetector receiver according to claim 1 , further comprising an upper layer comprising one of a p-doped material or an n-doped material covering the photodetector sections; and
a substrate, which is p-doped or n-doped, supporting the photodetector sections;
wherein the upper layer, the photodetector sections, and the substrate form a PIN junction.
3 . The WDM photodetector receiver according to claim 1 , wherein each photodetector section has substantially a same width, and wherein each photodetector section has a different thickness.
4 . The WDM photodetector receiver according to claim 1 , wherein each photodetector section is isolated electrically from each other via an insulating segment.
5 . The WDM photodetector receiver according to claim 4 , wherein each insulating segment comprises an implantation of H+ between adjacent photodetector sections.
6 . The WDM photodetector receiver according to claim 1 , wherein the cascaded-bandgap waveguide photodetector sections are configured such that an optical path entering the WDM photodetector receiver enters a cascaded-bandgap waveguide photodetector section having a lowest wavelength among the cascaded-bandgap waveguide photodetector sections before entering the other cascaded-bandgap waveguide photodetector sections.
7 . The WDM photodetector receiver according to claim 1 , wherein each cascaded-bandgap waveguide photodetector section is on a different portion of a substrate adjacent to each other arranged from lowest wavelength to highest wavelength.
8 . The WDM photodector receiver according to claim 1 , wherein the WDM photodetector receiver is optically connected to a transmitter via an optical network.
9 . A method of fabricating a wavelength division multiplexor (WDM) photodetector receiver, comprising:
a) providing a substrate;
b) providing a plurality of pairs of selective mask stripes with a trench therebetween on the substrate, each pair of mask stripes having a different width;
c) providing an absorbing material in each trench forming a plurality of photodetector sections at a same time, whereby the different width of each pair of mask stripes results in a different thickness of each photodetector section and a different bandgap of each photodetector section;
d) separating the plurality of photodetector sections; and
e) connecting the plurality of photodetector sections into concatenated photodetector sections forming a single elongated optical waveguide.
10 . The method according to claim 9 , wherein the absorbing material comprises multiple quantum well (MQW) absorbing media.
11 . The method according to claim 10 , wherein step c) includes selective area growth (SAG) by metalorganic vapor phase epitaxy (MOVPE).
12 . The method according to claim 9 , further comprising covering the optical waveguide with an upper layer comprising one of a p-doped material or an n-doped material;
wherein the substrate is p-doped or n-doped; and
wherein the upper layer, the optical waveguide and the substrate comprise a PIN junction.
13 . The method according to claim 9 , wherein step e) includes positioning a waveguide-defining mask over the absorbing material forming the plurality of photodetector sections and etching each side thereof to form the single optical waveguide.
14 . The method according to claim 9 , wherein step b) includes forming each trench about a same width.
15 . The method according to claim 9 , wherein step b) comprises coating the substrate with a masking material, and selectively etching the plurality of pairs of selective mask stripes from the masking material.
16 . The method according to claim 9 , wherein further comprising implanting H+ between adjacent photodetector sections for electrically insulating each photodetector section.
17 . The method according to claim 9 , further comprising configuring the bandgap of each photodetector section based on an operating temperature range of the WDM photodetector receiver.