Noise Equivalent Power Optimization of Graphene- Superconductor Optical Sensors in the Current Bias Mode

In this paper, the noise equivalent power (NEP) of an optical sensor based on graphene-superconductor junctions in the constant current mode of operation has been calculated. Furthermore, the necessary investigations to optimize the device noise with respect to various parameters such as the operating temperature, magnetic field, device resistance, voltage and current bias have been presented. By simultaneously solving the free energy and charge carrier density equations of graphene at low temperature, the specific heat, thermal interaction of electron-phonon and current responsivity of the sensor have been calculated. Using these parameters, the noise equivalent power of the device has been obtained. The results show that the behavior of device NEP by increasing the magnetic field at a constant temperature is at first ascending and then descending. The NEP value for different temperatures, up to T=80K, has an increasing behavior and then by further increasing the temperature, the NEP will show decreasing behavior which is also dependent on the value of the magnetic field. The NEP value is directly related to the device voltage and current values, therefore by increasing the voltage and current, the NEP will increase. Our investigations show that at the constant current bias mode of operation, the final device NEP is independent of the device resistance.