Method for detecting low-power optical signal with high sensitivity

Patent metadata

Field	Value
Publication number	US-2022075115-A1
Application number	US-202017012629-A
Country	US
Kind code	A1
Filing date	Sep 4, 2020
Priority date	Sep 4, 2020
Publication date	Mar 10, 2022
Grant date	—

Abstract

A method for making a pair of photodiodes to detect low-power optical signal includes providing a waveguide including one or more branches in a silicon photonics substrate to deliver an input optical signal to the silicon photonics integrated circuit; forming a pair of nearly redundant photodiodes in silicon photonics platform in the silicon photonics substrate. coupling a first one of the pair of nearly redundant photodiodes optically to each of the one or more branches for receiving the input optical signal combined from all of the one or more branches; coupling a second one of the pair of nearly redundant photodiodes electrically in series to the first one of the pair of nearly redundant photodiodes; and drawing a current from the first one of the pair of nearly redundant photodiodes under a reversed bias voltage applied to the pair of nearly redundant photodiodes.

First claim

1 - 20 . (canceled)

21 . A circuit for detecting an optical signal transmitted via a first waveguide, the circuit comprising:
a photonics substrate; a first photodiode formed in the photonics substrate and coupled to the first waveguide, the first photodiode configured to receive from the first waveguide a portion of the optical signal transmitted via the first waveguide and to generate a first current based on the optical signal; and a second photodiode formed in the photonics substrate without being coupled to the first waveguide, the second photodiode being configured to output a second current without receiving a portion of the optical signal, the second current corresponding to a dark current induced in the second photodiode, the circuit being configured to subtract the second current from the first current to generate an output signal corresponding to a difference between the first current and the second current.

22 . The circuit of claim 21 , the first photodiode and the second photodiode forming a close-neighbor pair.

23 . The circuit of claim 22 , the second photodiode being located within 500 nm of the first photodiode in the photonics substrate.

24 . The circuit of claim 23 , the first photodiode and the second photodiode being formed in the photonics substrate under a same CMOS process.

25 . The circuit of claim 24 , the dark current induced in the second photodiode being substantially the same as a dark current induced in the first photodiode.

26 . The circuit of claim 21 , the first photodiode being coupled to the first waveguide via a first tap coupler.

27 . The circuit of claim 26 , the first photodiode being coupled to the first waveguide via the first tap coupler, a second tap coupler, and a splitter.

28 . The circuit of claim 21 , the second photodiode being coupled in series with the first photodiode.

29 . The circuit of claim 28 , the circuit generating the output signal at a node between the first photodiode and the second photodiode.

30 . The circuit of claim 29 , the output signal corresponding to a photocurrent induced in the first photodiode.

31 . The circuit of claim 21 , the second photodiode not being coupled to the first photodiode.

32 . The circuit of claim 31 , the second photodiode having a same reverse bias condition as the first photodiode.

33 . The circuit of claim 32 , the second photodiode being connected to a same reverse bias voltage as the first photodiode.

34 . The circuit of claim 33 , the output signal corresponding to a difference between an output current of the first photodiode and an output current of the second photodiode.

35 . The circuit of claim 34 , the output current of the first photodiode being a photocurrent induced in the first photodiode and a dark current induced in the first photodiode, and the output current of the second photodiode being the dark current induced in the second photodiode.

36 . A method for detecting an optical signal transmitted via a waveguide, the method comprising:
receiving, via a waveguide, a portion of the optical signal at a first photodiode formed in a photonics substrate; generating a first current based on the optical signal using the first photodiode; using a second photodiode formed in the without being coupled to the waveguide, outputting a second current without receiving a portion of the optical signal the second current corresponding to a dark current induced in the second photodiode; and subtracting the second current from the first current to generate an output signal corresponding to a difference between the first current and the second current.

37 . The method of claim 36 , further comprising forming the second photodiode within 500 nm of the first photodiode under a same CMOS process such that the dark current induced in the second photodiode is substantially the same as a dark current induced in the first photodiode.

38 . The method of claim 36 , further comprising coupling the second photodiode in series with the first photodiode.

39 . The method of claim 36 , further comprising connecting the second photodiode to a same reverse bias voltage as the first photodiode.

40 . The method of claim 39 , further comprising generating the output signal based on a difference between an output current of the first photodiode and an output current of the second photodiode, the output current of the first photodiode being a photocurrent induced in the first photodiode and a dark current induced in the first photodiode, and the output current of the second photodiode being the dark current induced in the second photodiode.

Assignees

• Inphi Corp

Inventors

• Lin Jie
• Kato Masaki
• Tourette Bruno
• Taylor Brian

Classifications

• H04B10/691 Primary

  Arrangements for optimizing the photodetector in the receiver · CPC title

• H04B10/6911

  Photodiode bias control, e.g. for compensating temperature variations · CPC title

• H04B10/697

  Arrangements for reducing noise and distortion · CPC title

• G02B6/12019 Primary

  characterised by the optical interconnection to or from the AWG devices, e.g. integration or coupling with lasers or photodiodes (coupling integrated waveguide to fibre G02B6/30, to optoelectronic element G02B6/42; monolithic integration of integrated waveguides with other optical elements G02B6/12004) · CPC title

• H04B10/6165

  Estimation of the phase of the received optical signal, phase error estimation or phase error correction · CPC title