VCSEL collimation using self-aligned integrated polymer microlenses

Abstract

We report on the design and fabrication of polymer microlenses fabricated on patterned SU-8 layers in view of integrating microlenses on VCSEL arrays for laser beam shaping. For a standard top-emitting VCSEL, the lens has to be fabricated on a thick intermediate layer (pedestal) whose optimal thickness can be modelled as a function of the initial and of the aimed optical properties of the VCSEL beam. In this work, pedestals are fabricated with SU-8, which is a negative-tone photoresist transparent at the lasing wavelength. Lens deposition is realized using a robotized silicon microcantilever spotter technique after a simple SU-8 photolithography step in order to define high aspect ratio cylindrical pedestals with wide range diameters [30-140µm]. The effect of pedestal diameter on the final contact angle and curvature radius has been investigated using non contact optical profilometry and scanning electron microscopy. We show that this technique leads to a complete delimitation of the polymer droplets and to a better control of the final lens size. Moreover, lens positioning is fully ensured by the self-alignment of the droplet with the pillar center and consequently with the VCSEL source, and allows for meeting the stringent requirements on alignments.

Comparative study of soft thermal printing and lamination of dry thick photoresist films for the uniform fabrication of polymer MOEMS on small-sized samples

“…Therefore, it is not applicable to small and/or non-circular samples. Nevertheless, this method can be combined with an artificial increase of the sample surface by temporarily gluing it near surrounding pieces of sample (with the same thickness) on an adhesive support just before the spin-coating step [14]. In this way, the edge beads can extend the boundaries, provided close contact is obtained between the sample and the surrounding pieces; however, this is only applicable to rectangular samples.…”

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

“…These holes were created during the second UV exposure, at the same time the thin membrane was formed [see Fig. 2(d)], by taking advantages of proximity effects occurring inside the micrometer-scale patterns [51]. Therefore, no additional step was necessary.…”

Implementation of Integrated VCSEL-Based Optical Feedback Interferometry Microfluidic Sensor System with Polymer Microoptics

“…To reduce this value, we integrated a polymer collimation microlens directly above the chip after the dicing step. It was composed of a microlens deposited on a pedestal with a high aspect ratio [20] and a typical height of at least 100 µm. The micro-scale component dimensions (pedestal diameter and height, lens radius of curvature, and height) were optimized using the ZEMAX optical software.…”