New method doubles and accelerates thermal tuning of optical chips, supporting two current and voltage regulation methods

Silicon based quantum chip technology is one of the hot research directions in the field of integrated photonics. Thanks to compatibility with CMOS technology and silicon material characteristics, silicon-based integrated optical chips and devices have many advantages such as low cost, small size, low power consumption, and high integration, providing an ideal platform for large-scale optical computing, optical quantum computing, and information processing applications.

The Mach Zehnder interferometer (MZI) is a core device for high-precision programming operations in optical (quantum) computing chips. By combining and modulating the MZI and phase shifter, the key step of quantum state encoding can be completed, improving the information processing capability of optical quantum chips.

Specifically, the experimenter adjusts the phase difference of the transmitted light in the upper and lower arms of the MZI by applying different currents and voltages, thereby changing the intensity and phase of the output light, resulting in interference and achieving control of the optical path. To maximize the accuracy of chip calculations, it is necessary to accurately find the functional relationship between the phase shifter and the driving voltage and current. With the sharp increase in the number of connected MZIs on the chip, the combination of current, voltage, and phase shifter results in an exponential increase. Therefore, it is particularly important to find an efficient and feedback based current and voltage regulation method for phase shifters.

Thermal tuning test plan for MZI silicon polishing chip
The Sizhen programmable multi-channel current (voltage) source has a compact size and can achieve up to 64 channels of high-precision constant current and constant voltage output. The experimenter connected the current and voltage source to the PCB download adapter board through a shielded cable via SCSI, which can simultaneously apply appropriate voltage or current to 64 channels and adjust to obtain the desired optical signal. The loading values of each channel are initially random, and the experimenter finds the appropriate value through each iteration of the feedback function to achieve fast switching of current and voltage setting values. Among them, the maximum single channel current value of the series products can reach 100mA.

This solution supports two current and voltage regulation methods:
1. Manual adjustment: Directly input indicators through upper computer software
2. Python instruction automation control: The current and voltage source is programmed in Python to transmit control signals to the chip, then the PD value is detected and fed back to the current and voltage source through computer coding to change the control signal until the desired result is obtained.

Figure (a) shows a chip structure that can achieve any unitary transformation, and Figure (b) shows a chip structure that can achieve any two bit quantum operation, integrating a large number of MZI devices on the chip

Thermal tuning testing scheme for MZI silicon zenith computing chip

Source: Guangxing Tianxia