Device for converting a photonic signal, associated lidar and method

A device for converting a photonic signal to be analyzed, the conversion device including:—a photonic-electric conversion element, and—an electronic processing device, the conversion element including a splitter having two outputs connected to a first output branch and to a second output branch, respectively, the splitter including one or two inputs for receiving one or two input photonic signals, respectively, the splitter mixing the input photonic signals in the case where two inputs are present, the single received photonic input signal or the mixing of the two received photonic signals corresponding to a photonic signal to be analyzed, the splitter leading a first part of the photonic signal to be analyzed to the first output branch and leading a second part of the photonic signal to be analyzed to the second output branch, the conversion elements being configured for imposing, via the splitter, a phase shift of approximately 180 degrees between the first and the second portions of the photonic signal to be analyzed, each first or second output branch including a waveguide portion and a photodiode, each photodiode being configured for generating a respective first electrical current in response to receiving the first or second part of the photonic signal to be analyzed, each output branch being configured for generating at the output, a second electrical current having a value equal to or a multiple of a value of the first electrical current of the output branch considered, the processing device comprising an amplifier configured for generating at least one output signal according to a difference between the values of the two second electrical currents, a gain being defined for each output branch, the gain being a coefficient of proportionality between the value of the second electrical current of the output branch considered and a photonic power of the first or second part of the photonic signal to be analyzed, received by said output branch, the conversion device including at least one electronically controlled adjustment element, apt to modify one of the gains, the processing device including a first regulation loop comprising a low-pass filter and a device for controlling each adjustment element, the regulation loop receiving said output signal from said amplifier and producing an electrical control signal for each adjustment element so as to regulate the mean value of each output signal to a predefined setpoint value corresponding to the equalization of the DC components of the values of the two second electrical currents, the amplifier being a differential amplifier having a first input and a second input, at least one adjustment element including a current splitter, the current splitter being positioned between a photodiode of a given branch and an intermediate point electrically connected to a respective input of the differential amplifier, the current splitter being configured for modifying a coefficient of proportionality between the values of the first current and of a second current of said given branch, the current splitter including a first terminal connected to the intermediate point, a second terminal connected to the anode or the cathode of one of the photodiodes and a third terminal connected to a point having a fixed electrical potential, and the current splitter being configured for transmitting to the first terminal, a part of a current received from the second terminal and for transmitting to the third terminal another part of the current received from the second terminal, the current splitter including a first transistor connected to the second terminal and to the third terminal, a second transistor connected to the first terminal and to the second terminal, and a resistor between the source of the first transistor and the second terminal;

• the gate of the first transistor being configured for receiving a voltage delivered by said control device, while a constant electrical potential is applied to the gate of the second transistor.