Photonic integrated circuit temporal and frequency dispersion squint correction for optical phased array
An apparatus includes a photonic integrated circuit having an optical phased array and multiple arms. The optical phased array includes multiple unit cells, and each unit cell includes an antenna element configured to transmit or receive optical signals. The multiple arms are configured to modify the optical signals transmitted or received by the optical phased array. Each arm is controllable to provide at least one of temporal squint correction and frequency dispersion squint correction. The photonic integrated circuit may include electro-optic modulators, and the electro-optic modulators may be configured to provide controllable delays to the optical signals transmitted or received by the optical phased array. The photonic integrated circuit may include dispersive compensation elements, and the dispersive compensation elements may be configured to use controllable phase-frequency relationships to adjust the optical signals transmitted or received by the optical phased array in order to provide frequency dispersion squint correction.
1 . An apparatus comprising:
a photonic integrated circuit comprising:
an optical phased array comprising multiple unit cells, each unit cell comprising:
an antenna element configured to transmit optical signals through free space or receive optical signals through free space; and
a cascaded arrangement of modulators, the cascaded arrangement of modulators including multiple modulators having different response characteristics, the cascaded arrangement of modulators configured to provide controllable phase and dispersion control to the optical signals;
a digital read in integrated circuit (DRIIC) layer comprising multiple DRIIC cells, each DRIIC cell comprising:
a demultiplexer configured to select a value associated with a stream of array phase shifts received by the demultiplexer;
a register configured to receive an indication of the value selected by the demultiplexer and output the value; and
a first amplifier and a second amplifier configured to receive the value from the register and, based on the value, control at least one modulator of the cascaded arrangement of modulators of a respective unit cell of the optical phased array; and
multiple arms configured to modify the optical signals transmitted or received by the optical phased array, wherein each arm is controllable to provide step-wise compensation of temporal squint and step-wise compensation of frequency dispersion squint, and wherein each arm comprises a photodetector configured to output a sample of an optical signal associated with that arm, the samples used to phase-lock the arms with respect to one another.
2 . The apparatus of claim 1 , wherein the photonic integrated circuit further comprises semiconductor optical amplifiers configured to amplify the optical signals transmitted or received by the optical phased array, the multiple arms of the photonic integrated circuit including the semiconductor optical amplifiers.
3 . The apparatus of claim 2 , wherein:
the photonic integrated circuit further comprises electro-optic modulators optically coupled to the semiconductor optical amplifiers, the multiple arms of the photonic integrated circuit further including the electro-optic modulators; and
the electro-optic modulators are configured to provide controllable delays to the optical signals transmitted or received by the optical phased array.
4 . The apparatus of claim 3 , wherein the controllable delays of the electro-optic modulators are associated with corresponding delays in supercells of the photonic integrated circuit, each supercell comprising a subset of the unit cells.
5 . The apparatus of claim 2 , wherein:
the photonic integrated circuit further comprises dispersive compensation elements optically coupled to the semiconductor optical amplifiers, the multiple arms of the photonic integrated circuit further including the dispersive compensation elements; and
the dispersive compensation elements are configured to use controllable phase-frequency relationships to adjust the optical signals transmitted or received by the optical phased array in order to provide frequency dispersion squint correction.
6 . The apparatus of claim 5 , wherein the controllable phase-frequency relationships of the dispersive compensation elements are associated with corresponding phase-frequency relationships in supercells of the photonic integrated circuit, each supercell comprising a subset of the unit cells.
7 . The apparatus of claim 1 , wherein each unit cell further comprises a phase modulator configured to modify a phase of the optical signals being transported through a signal pathway of the unit cell.
8 . The apparatus of claim 1 , wherein one or more of the multiple modulators is a silicon-based resonant micro-ring modulator between about five microns and about six microns in diameter.
9 . The apparatus of claim 1 , wherein the value corresponds with output voltages to be provided by the first amplifier and the second amplifier to the at least one modulator.
10 . A method comprising:
transmitting optical signals through free space or receiving optical signals through free space using a photonic integrated circuit comprising a digital read in integrated circuit (DRIIC) layer and an optical phased array, the optical phased array comprising multiple unit cells, each unit cell comprising:
an antenna element that transmits or receives optical signals; and
a cascaded arrangement of modulators, the cascaded arrangement of modulators including multiple modulators having different response characteristics, the cascaded arrangement of modulators configured to be controlled by a DRIIC cell of the DRIIC layer to provide controllable phase and dispersion control to the optical signals
wherein the DRIIC cell comprises:
a demultiplexer that selects a value associated with a stream of array phase shifts received by the demultiplexer;
a register that receives an indication of the value selected by the demultiplexer and outputs the value; and
a first amplifier and a second amplifier that receive the value from the register and, based on the value, control at least one modulator of the cascaded arrangement of modulators of the unit cell;
controlling multiple arms of the photonic integrated circuit to modify the optical signals transmitted or received by the optical phased array, wherein each arm is controllable to provide step-wise compensation of temporal squint and step-wise compensation of frequency dispersion squint; and
phase-locking the arms with respect to each other using samples of the optical signals provided by photodetectors in the arms.
11 . The method of claim 10 , wherein the photonic integrated circuit further comprises semiconductor optical amplifiers that amplify the optical signals transmitted or received by the optical phased array, the multiple arms of the photonic integrated circuit including the semiconductor optical amplifiers.
12 . The method of claim 11 , wherein:
the photonic integrated circuit further comprises electro-optic modulators optically coupled to the semiconductor optical amplifiers, the multiple arms of the photonic integrated circuit further including the electro-optic modulators; and
the electro-optic modulators provide controllable delays to the optical signals transmitted or received by the optical phased array.
13 . The method of claim 12 , wherein the controllable delays of the electro-optic modulators are associated with corresponding delays in supercells of the photonic integrated circuit, each supercell comprising a subset of the unit cells.
14 . The method of claim 11 , wherein:
the photonic integrated circuit further comprises dispersive compensation elements optically coupled to the semiconductor optical amplifiers, the multiple arms of the photonic integrated circuit further including the dispersive compensation elements; and
the dispersive compensation elements use controllable phase-frequency relationships to adjust the optical signals transmitted or received by the optical phased array in order to provide frequency dispersion squint correction.
15 . The method of claim 14 , wherein the controllable phase-frequency relationships of the dispersive compensation elements are associated with corresponding phase-frequency relationships in supercells of the photonic integrated circuit, each supercell comprising a subset of the unit cells.
16 . An apparatus comprising:
a photonic integrated circuit comprising:
a digital read in integrated circuit (DRIIC) layer; and
an optical phased array comprising multiple unit cells, each unit cell comprising:
means for transmitting optical signals through free space or receiving optical signals through free space; and
means for providing controllable phase and dispersion control to the optical signals, the means controlled by a respective DRIIC cell of the DRIIC layer;
means for modifying the optical signals transmitted or received by the optical phased array to provide step-wise compensation of temporal squint and step-wise compensation of frequency dispersion squint; and
means for outputting samples of the optical signals, the samples used to phase-lock the optical signals with respect to one another,
wherein each of the DRIIC cells comprises:
a demultiplexer configured to select a value associated with a stream of array phase shifts received by the demultiplexer;
a register configured to receive an indication of the value selected by the demultiplexer and output the value; and
a first amplifier and a second amplifier configured to receive the value from the register and, based on the value, control the means for providing controllable phase and dispersion control to the optical signals.
17 . The apparatus of claim 16 , wherein the photonic integrated circuit further comprises means for amplifying the optical signals transmitted or received by the optical phased array.
18 . The apparatus of claim 17 , wherein the photonic integrated circuit further comprises means for providing controllable delays to the optical signals transmitted or received by the optical phased array.
19 . The apparatus of claim 17 , wherein the photonic integrated circuit further comprises means for providing dispersive compensation to the optical signals transmitted or received by the optical phased array.
20 . The apparatus of claim 16 , wherein each unit cell further comprises means for modifying a phase of the optical signals being transported through a signal pathway of the unit cell.