Electrical self-modulation of optical sensors for light power measurement in chemical applications by phase detection technique

High-Sensitivity High-Resolution Optical Phase Shift Detection Technique Using a Si Photodiode Operating in Photovoltaic Mode

“…These experimental results demonstrate that for the phase shift detection system with the Si PD in photovoltaic mode it is possible to achieve an improvement of the detection sensitivity of about one order of magnitude (i.e., 7.6) with respect to the best results presented in [21] and a strong enhancement of more than two orders of magnitude (i.e., 258) with respect to the best performances obtained with the Si PD operating in photoconductive mode [20]. Furthermore, considering the 0.01° phase resolution of the employed lock-in amplifier, the highest achieved sensitivity equal to 3100°/µW corresponds to the best resolution of the laser power variation detection of about 3pW.…”

“…Furthermore, for a comparison with the results presented in [20], Figure 2 reports also the best phase shift variation range obtained by employing the phase shift detection technique using the Si PD operating in photoconductive mode. In this case, the measurements have been performed by using the Section (b) of Figure 1 with a DC reverse bias voltage V R =9V superimposed to the sinusoidal voltage signal V BIAS (f 0 ) with an amplitude equal to ±50mV at the modulating frequency f 0 =77Hz [20].…”

“…In this case, the measurements have been performed by using the Section (b) of Figure 1 with a DC reverse bias voltage V R =9V superimposed to the sinusoidal voltage signal V BIAS (f 0 ) with an amplitude equal to ±50mV at the modulating frequency f 0 =77Hz [20]. The total achieved phase shift variation range is equal to 3.8° (i.e., from 34.79° to 38.59°) for a total laser power variation of about 300nW corresponding to the best detection sensitivity equal to 12°/µW.…”

“…Recently, it has been demonstrated that variations of the light power due to any kind of interaction with matter can be evaluated by measuring the phase shift between the electrical signal generated by the Si PD (i.e., the input signal) and a suitable reference signal at a specific modulating frequency with the Si PD operating in both photoconductive and photovoltaic regimes [19][20][21]. This novel detection method has the advantage to be independent from the amplitude of both the input and reference signals and does not suffer of any fullscale limitations.…”

Very high‐sensitivity tunable phase detection of light power variations using electrical modulation of Si‐photodiode in photovoltaic regime

“…On the other hand, the phase shift measurement between an input and reference signals is independent of their amplitudes, does not suffer from the full-scale limitations and the initial phase difference can be also easily zeroed. These characteristics open up the possibility to achieve innovative detection systems with very high resolution and sensitivity [4][5][6]. In this Letter, we propose the use of a silicon (Si)-photodiode (Si-PD) operating in photovoltaic mode as a tunable very high-sensitivity phase detector of light power variations.…”