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

Abstract

Using the optical feedback interferometry (OFI) technique, we demonstrated a miniaturized and compact sensor system based on a dedicated optical source for flowmetry at the micro-scale. In the system, polymer microlenses were integrated directly on a VCSEL (vertical-cavity surface-emitting laser) chip and the microfluidic channel chip surface using polymer-based micro-fabrication technologies. In particular, at a post-process stage, we integrated a collimation lens on a VCSEL chip of small dimensions (200 µm × 200 µm × 150 µm). This process was enabled by the soft-printing of dry thick resist films and through direct laser writing technology. We performed flow rate measurements using this new compact system, with a conventional bulk glass lens configuration for system performance evaluation. A maximum 33 dB signal-to-noise ratio was achieved from this novel ultra-compact system. To our knowledge, this is the highest signal level achieved by existing OFI based flowmetry sensors.

Direct 3D-printing of microlens on single mode polarization-stable VCSEL chip for miniaturized optical spectroscopy

“…As above-mentioned, a first method was successfully developed by the authors to reduce the beam divergence of similar chips to ∼3 deg (full angle at 1/e2). This method required, however, three successive fabrication steps: (i) soft-thermal printing of several dry resist films, (ii) UV direct laser writing of a cylindrical pedestal, and (iii) inkjet printing of droplet to form a hemispherical lens on the pedestal surface 13 , 14 . With this method, only discrete values of pedestal heights and ink droplets numbers could be chosen.…”

“… – 13 The authors recently developed an alternative method to enable similar integration on a single small-sized singlemode VCSEL chip. It is based on the use of thick dry resist films and direct UV laser writing 14 . In this work, we exploit the superior advantages of 3D two-photon-polymerization technique to fabricate a similar microlens at a post-mounting stage, but in a single step and with better control of the shape that can perfectly match the aimed design.…”

Inkjet‐Printed Microlenses Integrated onto Organic Photodiodes for Highly Accurate Proximity Sensing

“…[17] Moreover, digital printing technologies open new possibilities for customized micro-and nanooptics integrated with optoelectronic devices. For example, optical elements for improved light extraction in printed light-emitting devices [18] or inkjet printed microlens arrays for optical imaging systems [19][20][21][22][23][24][25][26] have been recently demonstrated. Only recently, Zhang et al presented an industrial compatible inkjet printing process with an optimized UV-curable ink achieving low shrinkage, high uniformity, and a high fill factor without surface structuring steps like photolithography.…”

“…Only recently, Zhang et al presented an industrial compatible inkjet printing process with an optimized UV-curable ink achieving low shrinkage, high uniformity, and a high fill factor without surface structuring steps like photolithography. [19] While applications with printed microlenses like flowmetry at the microscale [24] or the outcoupling of light on top of optical fibers [25,26] have been presented in the past, the combination with organic electronics technology is still due.…”

“…Moreover, digital printing technologies open new possibilities for customized micro‐ and nanooptics integrated with optoelectronic devices. For example, optical elements for improved light extraction in printed light‐emitting devices [ 18 ] or inkjet printed microlens arrays for optical imaging systems [ 19–26 ] have been recently demonstrated. Only recently, Zhang et al.…”