Optical Sensor with Frequency Output Based on Resonant Tunneling Diode

The paper shows the possibility of using a resonant tunneling diode as an optical sensor with a frequency output signal. The resonant tunneling diode was created on the basis of a quantum two-barrier heterostructure, which characterizes the existence of a negative differential resistance in the diode and its microwave properties in the entire radio frequency range. The diode acts both as a primary optical power sensor and as a microwave self-oscillator with an external oscillating LC system, where L and C are the equivalent inductance and equivalent capacitance of the oscillatory system. This greatly simplifies the design of the optical sensor. Using the principle of conversion “optical signal - frequency” can significantly improve the metrological performance of the device. A study of the characteristics of an optical sensor based on its equivalent circuit, which takes into account its inductive and capacitive properties, has been carried out. The current-voltage characteristic has a descending section, causes the appearance of a negative differential resistance, which compensates for energy losses in the oscillatory system of the sensor's self-oscillator. The mathematical model of the sensor is based on the Kirchhoff equations describing the behavior of its equivalent circuit. Analytical dependences of the change in sensor parameters on the effect of optical power on it, as well as the transformation and sensitivity functions, are obtained. It is shown that the main contribution to changes in the conversion functions and sensitivity of the sensor is made by the change in the negative differential resistance under the influence of optical power. This results in a shift in the instrument's output frequency. The sensitivity of the sensor varied from
$4.7\times 10^{7} \text{Hz}/\text{mW}$
to
$7.4\times 10^{7}\ \text{Hz}/\text{mW}$
in the optical power change range from 1 mW to 10 mW.