Multimode VCSELs for Self-Mixing Velocity Measurements

Abstract

In this paper, we present the feasibility of a laser Doppler velocimeter using self-mixing effect in low-cost strongly multimode VCSELs (AlGaAs). The prototype of velocity sensor demonstrates a 20dB signal-to-noise ratio over an amplification bandwidth of 10MHz allowing velocity measurements up to 8.5m.s −1 . The VCSEL-based self-mixing sensor has been characterized at various distances from the target, and with cooperative and non-cooperative surfaces. A characterization of the temperature sensitivity of the VCSEL-based velocimeter results is presented which demonstrates the great stability of the device over an important temperature range. A comparison between results obtained with strongly multimode VCSELs and Fabry-Pérot laser diodes in velocimetry applications is achieved. We finally discuss the intrinsic advantages of VCSELs in self-mixing applications as in particular for on-board sensors.

Photodiode-free Doppler velocimeter based on self-mixing effect in commercial VCSELs

“…That low power dissipation allows VCSELs to exhibit a high reliability (up to 10 5 hours). Second, their lasing frequency is less sensitive to temperature variations than traditional edge emitters [9]. It has been demonstrated experimentally [10] and theoretically by [11] that despite the high reflectivity of the DBRs, VCSELs shows a similar sensitivity to optical feedback as edge emitters in reason of the shortness of the internal cavity.…”

“…It has been demonstrated experimentally [10] and theoretically by [11] that despite the high reflectivity of the DBRs, VCSELs shows a similar sensitivity to optical feedback as edge emitters in reason of the shortness of the internal cavity. Even usual commercial VCSELs which exhibit a complex and unstable distribution of transverse modes are well suited to design velocity sensors [9], despite additional effects due to multiple interferences between transverse modes [5]. A limitation encountered with VCSELs in SMI technique is due to the epitaxial growth of such laser diode that exclude to dispose of a photodiode at the back facet of the device as it is with traditional edge emitters with a high coupling efficiency.…”

A miniaturized VCSEL-based system for optical sensing in a microfluidic channel

“…This allows for the detection of the VCSEL beam absorption in presence of a cell. It is worth noting that VCSEL internal photo-detection properties could be also exploited to lead to a even more compact system and to avoid alignments step [5][6] [7]. In this system, the main issue concerns VCSEL beam focusing to beam widths in the range 10 to 20µm, combined to working distances higher than 100µm.…”

Advances in Polymer-Based Optical MEMS Fabrication for VCSEL Beam Shaping

“…V ERTICAL cavity surface emitting lasers (VCSELs) are currently the first choice in photonic devices for an increasing range of applications, including short-distance data communications, optical sensors and laser printers [1]- [3], as well as flow cytometry [4], [5], parallel optical trapping [6], nano-bio-sensing [7] and optical probe microscopy [8]. This success is due to the devices' outstanding characteristics, such as parallel operation, low threshold current, high modulation rate and a circularly symmetric emitted beam.…”