To carry out automatic bias control to an optical modulator without a dither signal with reduced cost, an optical transmitter comprises a light source configured to output a light, an optical first modulator configured to modulate the light and output a first modulated optical signal, a DC component detector configured to detect a DC component of the first modulated optical signal and a controller configured to apply a first specific bias voltage identified based on the DC component to the optical first modulator.

Disclosed is an optical assembly having a first variable transmission layer comprising a first electro-optically active material between a first pair of substrates, a second variable transmission layer comprising a second electro-optically active material between a second pair of substrates, and an electronically switchable birefringent layer, that is capable of altering the phase of incident light, situated between the first and second variable transmission layers. The layers are arranged such that light passing through the optical assembly can be altered based on the voltage applied to each layer. The light transmission levels can be altered between maximally transmissive, minimally transmissive, and semi-transparent levels between the maximally and minimally transmissive levels.

To suppress the deterioration of signal quality in an optical signal, a LiDAR device comprises: a signal output means 20 for outputting a first electric signal in a first period, reducing the amplitude of the first electric signal outside the first period, and then outputting a second electric signal; a modulator 30 which outputs an optical signal modulated on the basis of the first electric signal or the second electric signal; and a control means 40 for applying, to the modulator 30, a bias voltage based on the optical signal modulated on the basis of the first electric signal.

There are disclosed an electrically tunable metasurface and a method for modulating propagation characteristics of an incident plane wave. The electrically tunable metasurface comprising: i) a plurality of scatterer rings, each one of the plurality of scatterer rings including bow-tie radiator elements, the bow-tie radiator elements in a corresponding scatterer ring having a same geometric configuration; and ii) a plurality of electrodes, each electrode being configured to provide a biasing voltage to the corresponding scatterer ring. The method comprising: i) receiving, by an electrically tunable metasurface, the incident plane wave; and ii) modulating the propagation characteristics of the incident plane wave by providing specific biasing voltage to the corresponding scatterer rings.

An optical transmitter includes an electro-optic modulator, a monitor circuit that monitors output light of the electro-optic modulator, and a processor that controls a bias voltage of the electro-optic modulator using a monitoring result of the monitor circuit, wherein the processor superimposes a first dither signal with a first frequency and a second dither signal with a second frequency different from the first frequency, onto one bias voltage in a time sharing manner, calculates a first control error based on a first component oscillating at the first frequency and a second control error based on a second component oscillating at the second frequency based on the monitoring result, and determines a control value for controlling the bias voltage using the first control error and the second control error.

An electro-absorption modulator (EAM) configured to receive light and output a modulated optical signal. The EAM may include a current source used to set a predetermined modulation performance and an output power of the EAM. The current source is set to provide a constant current and constant bias for the electro-absorption modulator, where the EAM automatically self-adjusts to detuning changes between the EAM and the optical light source to maintain a predetermined modulation performance and output power of the EAM.

An optical element is switchable between a first state having a first focal length and a second state having a second focal length. The optical element includes a first electrode layer, an insulation layer, a resistance layer, a liquid crystal layer, and a second electrode layer, which are arranged in order. An electric resistance ratio of the resistance layer increases from a central part to a peripheral part.

Various examples are provided related to adaptive photonic radio frequency (RF) spectral shapers. In one example, a RF spectral shaper includes processing circuitry that can generate finite impulse response (FIR) parameters based upon a target RF spectral response; an optical wave shaper that can generate a shaped interleaved comb carrier from a broadband optical signal based upon the FIR parameters; an electro-optic modulator (EOM) that can modulate an RF signal onto the shaped interleaved comb carrier to generate a modulated optical comb carrier; and a photodetector that can convert the modulated optical comb carrier back to an RF output signal. In another example, a method includes generating FIR parameters based upon a target RF spectral response; generating a shaped interleaved comb carrier from a broadband optical signal based upon the FIR parameters; and generating a modulated optical comb carrier by modulating an RF signal onto the shaped interleaved comb carrier.

An optical transmitter comprises a directly coupled MZ interferometer and driver circuit. The MZ interferometer comprises a pair of differentially driven MZ electrodes configured to impart RF signals to light travelling through respective arms of the interferometer, and to receive DC bias as a positive voltage via lower n-type cladding of the MZ interferometer. The lower n-type cladding is at a different positive DC potential to an upper plane RF ground of the MZ interferometer, but the lower n-type cladding and the upper plane RF ground have similar AC potential. The MZ interferometer also comprises a pair of resistors in series configured to provide differential RF termination of the MZ electrodes; and a capacitive coupling between a virtual ground formed at a centre point between the pair of resistors and an RF ground configured to provide common-mode RF termination. The DC supply for the driver circuit is applied to the centre point of the RF termination.

Devices, methods and systems for generating wideband, high-fidelity arbitrary radio frequency (RF) passband signals are described. A voltage tunable optical filter for arbitrary RF passband signal generation includes a first input configured to receive a broadband optical pulse train, a second input configured to receive a first control voltage representative of an amplitude signal, an electrooptic modulator to receive the broadband optical pulse train and the first control voltage, to modulate the broadband optical pulse train in accordance with the amplitude signal, and to produce two complementary optical outputs that form two arms of an interferometer, an optical delay component to impart an optical path difference into one of the complementary outputs of the electrooptic modulator, and a combiner or a splitter to receive two complementary optical outputs of the electrooptic modulator after impartation of the optical path difference and to produce an output interference pattern of fringes.