On-chip optical trapping and Raman spectroscopy using a TripleX dual-waveguide trap

Abstract

We present a new approach to the dual-beam geometry for onchip optical trapping and Raman spectroscopy, using waveguides microfabricated in TripleX technology. Such waveguides are box shaped and consist of SiO 2 and Si 3 N 4 , so as to provide a low index contrast with respect to the SiO 2 claddings and low loss, while retaining the advantages of Si 3 N 4 . The waveguides enable both the trapping and Raman functionality with the same dual beams. Polystyrene beads of 1 µm diameter can be easily trapped with the device. In the axial direction discrete trapping positions occur, owing to the intensity pattern of the interfering beams. Trapping events are interpreted on the basis of simulated optical fields and calculated optical forces. The average transverse trap stiffness is 0.8 pN/nm/W, indicating that a strong trap is formed by the beams emitted by the waveguides. Finally, we measure Raman spectra of trapped beads for short integration times (down to 0.25 s), which is very promising for Raman spectroscopy of microbiological cells.

TriPleX: a versatile dielectric photonic platform

“…The integration of TriPleX box shell geometry waveguides with microfluidic channels was applied in the demonstration of optical particle trapping in combination with Raman spectroscopy, which was realized in one of the MPW runs [83]. The optical trap was created by splitting the 785-nm optical signal by a 3-dB Y-junction over two excitation branches facing toward each other at the 5-μm-wide trapping and excitation region of the fluidic channel ( Figure 14).…”

Optical transport, lifting and trapping of micro-particles by planar waveguides

“…Waveguide loops with gap separation of 2-30 µm were demonstrated to precisely trap micro-spheres of different sizes and also red blood cells. The waveguide loop with gap can also be combined with a transverse microfluidic chamber, for delivering particles to the gap [11]. This approach, although it is fast, it is less predictable in which particles are trapped.…”

On-chip phase measurement for microparticles trapped on a waveguide

“…[1][2][3][4][5][6][7][8][9][10][11][12] Optical waveguides have an evanescent field that stretches about 250 nm from their surfaces. They are thus attractive devices for on-chip manipulation, detection and sorting of particles.…”

“…This was first demonstrated in 1992 by Kawata and Sugiura. A few on-chip detection methods have been demonstrated, including on-chip Ramanspectroscopy 9 and measuring the change in resonance frequency of a photonic crystal. Microparticles have been trapped and held at a specific location with a waveguide loop with an intentional gap.…”