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Université de Neuchâtel

Thermally activated solvent bonding of polymers

Ng, S. H. ; Tjeung, R. T. ; Wang, Z. F. ; Lu, A. C. W. ; Rodriguez, I. ; de Rooij, Nicolaas F.

In: Microsystem Technologies, 2008, vol. 14, no. 6, p. 753-759

We present a thermally activated solvent bonding technique for the formation of embedded microstructures in polymer. It is based on the temperature dependent solubility of polymer in a liquid that is not a solvent at room temperature. With thermal activation, the liquid is transformed into a solvent of the polymer, creating a bonding capability through segmental or chain interdiffusion at the...

Université de Neuchâtel

Development of a multi-layer microelectrofluidic platform

Ng, S. H. ; Wang, Z. F. ; Tjeung, R. T. ; de Rooij, Nicolaas F.

In: Microsystem Technologies, 2007, vol. 13, no. 11-12, p. 1509-1515

We report on recent advances in micro fabrication technology using micromoulding and high-aspect ratio structuring of photopolymer. The direct application is the realization of components for millimeter-size, ultrasonic piezoelectric motors. A new fabrication process using a thick epoxy-based material (SU-8) and the electroplating of nickel is demonstrated. Photopolymer structures have also been...

Université de Neuchâtel

Development of 1 × 4 MEMS-based optical switch

Wang, Z. F. ; Cao, W. ; Shan, X. C. ; Xu, J. F. ; Lim, S. P. ; Noell, Wilfried ; de Rooij, Nicolaas F.

In: Sensors and Actuators A: Physical, 2004, vol. 114, no. 1, p. 80-87

In this paper, a novel 1×4 optical switch has been developed based on the DRIE vertical mirror technology. Three microactuated vertical silicon mirrors and five tapered/lensed fibers were employed to perform the 1×4 switch function. The comb actuators drive the mirrors linearly into the optical path due to the electrostatic force. The tilted mirror with an angle of 22.5° made the layout of the...

Université de Neuchâtel

Phonon sidebands of intersubband absorption in AlGaN/GaN high-electron-mobility transistors

Wang, Z. ; Reimann, K. ; Woerner, M. ; Elsaesser, T. ; Hofstetter, Daniel ; Hwang, Jeff ; Schaff, William J. ; Eastman, Lester F.

In: Physica E: Low-dimensional Systems and Nanostructures, 2006, vol. 32, no. 1-2, p. 562-565

Femtosecond two-color pump-probe experiments in the mid-infrared are performed on intersubband transitions in a GaN/Al0.8Ga0.2N heterostructure. In these experiments, we observe around zero time delay distinct phonon sidebands, which disappear because of spectral diffusion with a time constant of 80 fs. The signal itself decays with a time constant of 380 fs. The independent...

Université de Neuchâtel

Femtosecond intersubband dynamics of electrons in AlGaN/GaN-based high-electron-mobility transistors

Wang, Z. ; Reimann, K. ; Woerner, M. ; Elsaesser, T. ; Hofstetter, Daniel ; Hwang, Jeff ; Schaff, William J. ; Eastman, Lester F.

In: Semiconductor Science and Technology, 2004, vol. 19, p. S463-S464

Ultrafast electron dynamics in the inversion layer of an AlGaN/GaN transistor is studied in pump–probe experiments with 50 fs mid-infrared pulses. Two-colour pump–probe measurements show an instantaneous transmission increase for all spectral positions of the probe, which demonstrates that homogeneous broadening is an important contribution to the total linewidth in this material. We observe...

Université de Neuchâtel

Ultrafast hole burning in intersubband absorption lines of GaN/AlN superlattices

Wang, Z. ; Reimann, K. ; Woerner, M. ; Elsaesser, T. ; Hofstetter, Daniel ; Baumann, E. ; Giorgetta, Fabrizio R. ; Wu, H. ; Schaff, W. J. ; Eastman, L. F.

In: Applied Physics Letters, 2006, vol. 89, no. 151103, p. 1-3

The authors present evidence for a distinct optical phonon progression in the nonlinear intersubband absorption spectra of electrons in a GaN/AlN superlattice. Femtosecond two-color pump-probe experiments in the near infrared show spectral holes separated by the longitudinal optical (LO) phonon frequency and a homogeneous line broadening of approximately 50 meV. The nonlinear bleaching signal...

Université de Neuchâtel

Optical Phonon Sidebands of Electronic Intersubband Absorption in Strongly Polar Semiconductor Heterostructures

Wang, Z. ; Reimann, K. ; Woerner, M. ; Elsaesser, T. ; Hofstetter, Daniel ; Hwang, J. ; Schaff, William J. ; Eastman, L. F.

In: Physical Review Letters, 2005, vol. 94, no. 037403, p. 1-4

We present the first evidence for a distinct optical phonon progression in the linear and nonlinear intersubband absorption spectra of electrons in a GaN/Al0.8Ga0.2N heterostructure. Femtosecond two-color pump-probe experiments in the midinfrared reveal spectral holes on different vibronic transitions separated by the LO-phonon frequency. These features wash out with a decay...