3D sensing is being widely adopted in consumer, industrial and automotive markets. As an illumination source, VCSELs provide a combination of high efficiency, miniaturized packaging, fast pulse rise times and minimal spectral shift with temperature. This paper will describe advances in VCSEL technology that address the requirements of 3D sensing and LiDAR applications. 3D Sensing based on structured light requires power efficient VCSELs with a narrow beam divergence, compatible with the optics that produce a spot pattern in the far field. Time of Flight or LiDAR also requires high power efficiency, as well as fast rise times for good resolution in the 3rd dimension. For consumer applications, compactness of the illumination module is important, while all versions of 3D sensing benefit from the VCSEL’s narrow spectrum and low spectral shift with temperature. In this paper we will describe recent advances in VCSEL technology that enable improvements in 3D sensing systems. This includes efficiency improvements (greater than 60% power conversion efficiency), multi-junction VCSEL designs (up to 5 junctions in a device), and flip-chip back-side emitting VCSELs that enable miniaturization of illumination modules and large-scale addressability. In addition, we will describe module level integration of illumination sources, particularly for Time of Flight (TOF) and LiDAR applications, that incorporate VCSEL, driver, monitor diode, eye safety measures and optics.
Vixar presents a novel monolithic tunable vertical cavity surface emitting laser (VCSEL) design with a demonstrated tunable wavelength range of 41 nm in the near-infrared. This design combines a microelectromechanical system (MEMS) top mirror over a gallium arsenide based VCSEL cavity, and a monolithic construction which side steps any complex external cavity structures needed for tuning. We will present results which show the electro-thermally tunable mirror physically and reproducibly moving up to 400 nm, which corresponds to potential tuning range of over 50 nm in output wavelengths. These results also illustrate the use of this single mode, continuous wave, tunable VCSEL as a light source for biological tomographic imaging. Data taken in collaboration with Notre Dame presents the use of such tunable light sources for diffuse optical spectroscopic imaging (DOSI) of breast tumors and other anomalous tissue inclusions. Previous work confirms the viability of this design as an optical source for DOSI instruments and the work presented here shows improved results with even greater tuning capabilities and higher optical power. In conjunction with past work centered at 775 nm, current work at 940 nm, and future proposed VCSEL examples at 905 nm, Vixar expects to show that this design is capable of supporting tomographic imaging spanning 765 -782 nm, and 885 – 955 nm in total. Above and beyond these immediate imaging goals, these results continue to enable future visions of many possible applications for which a monolithic tunable light source might be ideal.