OPTOMECHANICAL SENSOR BASED ON SILICON PHOTONICS PLATFORM
Since it is an ongoing effort, I am just posting some cool looking pictures here.
At late July 2023, finally received my first tape-out of silicon photonics chips. Looks nice under the microscope!
Spend time during July and August 2023 in the cleanroom doing DRIE(deep reactive ion etching) of the silicon chip
How sensitive can the sensor be?
We consider the two noise sources, namely thermal mechanical noise and quantum shot noise. The quantum shot noise descibes the randomness of the number of electrons generated at the photodetector, which at large number can be approximation as gaussian random process. Thus the higher the sensitivity of the optomechanical sensor, the lower the shot noise can be made.
This can be achieved via two means, either by increasing the optical detection sensitivity or the mechanical sensitivity. Optical detection sensitivity refers to the rate of change of the optical power with respect to effective index or optical path change. The mechanical sensitivity refers to the efficiency of the transfer of measurand to the changes either in its effective index or the optical path. The product of these two sensitivity gives the total optical sensitivity, dividing the shot noise with the sensitivity will give the quantum shot noise defined MDS. The value determines the best performance of your sensor. This poisson process, which underlies the fundamental quantum variation, sets the detection limit of the sensor.
The packaging and testing of optomechanical sensor
The targeted application of this sensor is for ultrasensitive measurement of seismic activities under harsh environment underground. So temperature survivability as well as mechanical robustness are our major concerns. Here an illustration of the package is envisioned that have integrated fiber optics connectors. Thus it enables "plug and play" , with the sensor securely sits within the protective metal shielding.