Ultrafast laser micro-nano structuring of transparent materials with high aspect ratio

Ultrafast lasers are ideal tools to process transparent materials because they spatially confine the deposition of laser energy within the material's bulk via nonlinear photoionization processes. Nonlinear propagation and filamentation were initially regarded as deleterious effects. But in the last decade, they turned out to be benefits to control energy deposition over long distances. These effects create very high aspect ratio structures which have found a number of important applications, particularly for glass separation with non-ablative techniques. This chapter reviews the developments of in-volume ultrafast laser processing of transparent materials. We discuss the basic physics of the processes, characterization means, filamentation of Gaussian and Bessel beams and provide an overview of present applications

Combinational Multiphoton Scanning Microscopy and Multiphoton Surgery of Mouse Arteries

Preliminary investigations were carried out in order to explore the potential of laser-stimulated capillary growth in a blood vessel-on-a-chip. To fulfill the project objective, a series of experiments in both directions of two photon fluorescence imaging and laser-semitransparent materials interaction were performed. A purpose-built two-photon fluorescence imaging resolution was tested by imaging 1 micron diameter fluorescent beads. Also, the potential of fluorescence imaging in the waveguide writing eld as well as the biological eld was studied. Further, for laser ablation on the mouse artery loaded in the microfluidic channel, the processing window was found such that the damage induced by femtosecond laser just a effects the artery, not the other interfaces of the microfluidic chip. At the end, the result of laser trepanning on the mouse artery wall combined with two photon fluorescence imaging was shown. These results will be useful for more advanced biological study such as angiogenesis.MAS

Silicon Ring Modulators for High-speed Optical Interconnects

This thesis presents research contributions in the area of ring modulator modeling, design, and characterization. These include small-signal modeling of the intracavity and the coupling modulated ring modulators, optimization of intracavity ring modulator rib-to-contact distance as well as proposal, design, and fabrication of PAM-N and QAM-N modulators. Accurate modeling of the ring modulator small-signal response is essential for designing a modulator. In this thesis, a closed-form expression for small-signal response of an intracavity ring modulator is derived and verified by measurement results. The pole-zero representation of the transfer function illustrates dependency of the ring modulator frequency response upon parameters such as electrical bandwidth, coupling condition, optical loss, and sign/value of the laser detunings. Using the developed small-signal model and through measurement of the fabricated intracavity ring modulators in IME A*Star process, electrical and optical trade-offs of rib-to-contact distance are analyzed. Key parameters such as extinction ratio, insertion loss, transmission penalty, and bandwidth are compared quantitatively. We show that at 4dB extinction ratio, decreasing the high doped region distance to rib from 800nm to 350nm increases the bandwidth by 3.8Ă while increasing the insertion loss by 8.4dB. Small-signal response of the coupling-modulated ring resonator is also obtained and is compared with the intracavity ring modulator response. Based on number of poles and zeros, it is shown that unlike the intracavity ring modulator, the coupling-modulated ring resonator does not have the optical bandwidth limitation. Coupling modulation in a ring resonator is then used to present a new method for optical PAM modulation. The response of this modulator is optimized in terms of linearity for both reverse and forward-biased cases. This modulator can operate for long haul communication with its data rate only limited by the MZI bandwidth. Lastly, a compact structure for DAC-free optical QAM modulation based on the coupling modulated ring resonator is proposed and fully analyzed where various key design considerations are discussed. Output level linearity is also studied where we show that linearity among levels is achievable with two segments in QAM-16 while an additional segment may be required in QAM-64.Ph.D.2018-11-20 00:00:0