Self-mixing sensing system based on uncooled vertical-cavity surface-emitting laser array: linking multichannel operation and enhanced performance

Abstract

We compare the performance of a self-mixing (SM) sensing system based on an uncooled monolithic array of 24×1 vertical-cavity surface-emitting lasers (VCSELs) in two modes of operation: single active channel and the concurrent multichannel operation. We find that the signal-to-noise ratio of individual SM sensors in a VCSEL array is markedly improved by multichannel operation, as a consequence of the increased operational temperature of the sensors. The performance improvement can be further increased by manufacturing VCSEL arrays with smaller pitch. This has the potential to produce an imaging system with high spatial and temporal resolutions that can be operated without temperature stabilization.

Effect of injection current and temperature on signal strength in a laser diode optical feedback interferometer

“…For an ideal laser diode, the amplitude of the LV signal does not depend on the injected current -quite unlike the amplitude of the PD signal in (8) [2]. Moreover, (16) suggests that the amplitude of the LV signal increases with temperature -a phenomenon which has been observed in experiment [3,6]. However, constant slope efficiency is often unrealistic in practice, especially for single-mode laser diodes where thermal effects have significant impact on the non-radiative recombination and spontaneous emission rates [19].…”

“…OFI signals can be acquired by two different means: (i) by observing power fluctuations in the light emitted by the rear facet of the laser diode with a monitoring photodiode (denoted here as the PD signal), or (ii) by amplifying voltage variations across the laser terminals (denoted here as the LV signal) [2]. The latter is the only viable measurement approach when a monitoring photodiode is not included in the laser diode package, for example when an array of laser diodes is used [3]. For both methods of signal acquisition, in order to achieve the best performance of the OFI sensor it is essential to maintain the signal-to-noise ratio (SNR) at a maximum.…”