Chalcogenide glasses are highly nonlinear optical materials which can be used for fabricating active and passive photonic devices. This thesis work deals with the fabrication of buried, three dimensional, channel waveguides in chalcogenide glasses, using ultrafast laser inscription technique. The femtosecond laser pulses are focused into rare earth ions doped and undoped chalcogenide glasses, few hundred microns below from the surface to modify the physical properties such as refractive index, density, etc. These changes are made use in the fabrication of active and passive photonic waveguides which have applications in integrated optics. The first chapter provides an introduction to the fundamental aspects of femtosecond laser inscription, laser interaction with matter and chalcogenide glasses for photonic applications. The advantages and applications of chalcogenide glasses are also described. Motivation and overview of the present thesis work have been discussed at the end. The methods of chalcogenide glass preparation, waveguide fabrication and characterization of the glasses investigated are described in the second chapter. Also, the details of the experiments undertaken, namely, loss (passive insertion loss) and gain measurements (active) and nanoindentation studies are outlined. Chapter three presents a study on the effect of net fluence on waveguide formation. A heat diffusion model has been used to solve the waveguide cross-section. The waveguide formation in GeGaS chalcogenide glasses using the ultrafast laser, has been analyzed in the light of a finite element thermal diffusion model. The relation between the net fluence and waveguide cross section diameter has been verified using the experimentally measured properties and theoretically predicted values. Chapter four presents a study on waveguide fabrication on Er doped Chalcogenide glass. The active and passive characterization is done and the optimal waveguide fabrication parameters are given, along with gain properties for Er doped GeGaS glass. A C-band waveguide amplifier has been demonstrated on Chalcogenide glasses using ultrafast laser inscription technique. A study on the mechanical properties of the waveguide, undertaken using the nanoindentation technique, is presented in the fifth chapter. This work brings out the close relation between the change in mechanical properties such as elastic modulus and hardness of the material under the irradiation of ultrafast laser after the waveguide formation. Also, a threshold value of the modulus and hardness for characterizing the modes of the waveguide is suggested. Finally, the chapter six provides a summary of work undertaken and also discusses the future work to be carried out.

Biological research and Clinical Diagnostics heavily rely on Optical Microscopy for analyzing properties of cells. The experimental protocol for con-ducting a microscopy based diagnostic test consists of several manual steps, like sample extraction, slide preparation and inspection. Recent advances in optical microscopy have predominantly focused on resolution enhancement. Whereas, the aspect of automating the manual steps and enhancing imaging throughput were relatively less explored. Cost-e ective automation of clinical microscopy would potentially enable the creation of diagnostic devices with a wide range of medical and biological applications. Further, automation plays an important role in enabling diagnostic testing in resource-limited settings. This thesis presents a novel optofluidics based approach for automation of clinical diagnostic microscopy. A system-level integrated optofluidic architecture, which enables the automation of overall diagnostic work- ow has been proposed. Based on the proposed architecture, three different prototypes, which can enable point-of-care (POC) imaging cytometry have been developed. The characterization of these prototypes has been performed. Following which, the applicability of the platform for usage in diagnostic testing has been validated. The prototypes were used to demonstrate applications like Cell Viability Assay, Red Blood Cell Counting, Diagnosis of Malaria and Spherocytosis. An important performance metric of the device is the throughput (number of cells imaged per second). A novel microfluidic channel design, capable of enabling imaging throughputs of about 2000 cells per second has been incorporated into the instrument. Further, material properties of the sample handling component (microfluidic device) determine several functional aspects of the instrument. Ultrafast-laser inscription (ULI) based glass microfluidic devices have been identi ed and tested as viable alternatives to Polydimethylsiloxane (PDMS) based microfluidic chips. Cellular imaging with POC platforms has thus far been limited to acquisition of 2D morphology. To potentially enable 3D cellular imaging with POC platforms, a novel slanted channel microfluidic chip design has been proposed. The proposed design has been experimentally validated by performing 3D imaging of fluorescent microspheres and cells. It is envisaged that the proposed innovation would aid to the current e orts towards implementing good quality health-care in rural scenarios. The thesis is organized in the following manner : The overall thesis can be divided into two parts. The first part (chapters 2, 3) of the thesis deals with the optical aspects of the proposed Optofluidic instrument (development, characterization and validations demonstrating its use in poc diagnostic applications). The second part (chapters 4,5,6) of the thesis details the microfluidic sample handling aspects implemented with the help of custom fabricated microfludic devices, the integration of the prototype, func-tional framework of the device. Chapter 2 introduces the proposed optofluidic architecture for implementing the POC tool. Further, it details the first implementation of the proposed platform, based on the philosophy of adapting ubiquitously available electronic imaging devices to perform cellular diagnostic testing. The characterization of the developed prototypes is also detailed. Chapter 3 details the development of a stand-alone prototype based on the proposed architecture using inexpensive o -the-shelf, low frame-rate image sensors. The characterization of the developed prototype and its performance evaluation for application in malaria diagnostic testing are also presented. The chapter concludes with a comparative evaluation of the developed prototypes, so far. Chapter 4 presents a novel microfludic channel design, which enables the enhancement of imaging throughput, even while employing an inexpensive low frame-rate imaging modules. The design takes advantage of radial arrangement of microfludic channels for enhancing the achievable imaging throughput. The fabrication of the device and characterization of achievable throughputs is presented. The stand-alone optofluidic imaging system was then integrated into a single functional unit, with the proposed microfluidic channel design, a viscoelastic effect based micro uidic mixer and a suction-based microfluidic pumping mechanism. Chapter 5 brings into picture the aspect of the material used to fabricate the sample handling unit, the robustness of which determines certain functional aspects of the device. An investigative study on the applicability of glass microfluidic devices, fabricated using ultra-fast laser inscription in the context of the microfluidics based imaging flow cytometry is presented. As detailed in the introduction, imaging in poc platforms, has thus far been limited to acquisition of 2D images. The design and implementation of a novel slanted channel microfluidic chip, which can potentially enable 3D imaging with simplistic optical imaging systems (such as the one reported in the earlier chapters of this thesis) is detailed. A example application of the proposed microfludic chip architecture for imaging 3D fluorescence imaging of cells in flow is presented. Chapter 6 introduces a diagnostic assessment framework for the use of the developed of m in an actual clinical diagnostic scenario. The chapter presents the use of computational signatures (extracted from cell images) to be employed for cell recognition, as part of the proposed framework. The experimental results obtained while employing the framework to identify cells from three different leukemia cell lines have been presented in this chapter. Chapter 7 summarizes the contributions reported in this thesis. Potential future scope of the work is also detailed.

Lasers find a wide range of applications in many areas including photo-biology, photo-chemistry, materials processing, imaging and telecommunications. However, the practical use of such sources is often limited by the bulky nature of existing systems. By fabricating channel waveguides in solid-state laser-gain materials more compact laser systems can be designed and fabricated, providing user-friendly sources. Other advantages inherent in the use of waveguide gain media include the maintenance of high intensities over extended interaction lengths, reducing laser thresholds. This thesis presents the development of Yb:tungstate lasers operating around 1μm in waveguide geometries. An Yb:KY(WO₄)₂ planar waveguide laser grown by liquid phase epitaxy is demonstrated with output powers up to 190 mW and 76 % slope efficiency. This is similar to the performance from bulk lasers but in a very compact design. Excellent thresholds of only 40 mW absorbed pump power are realised. The propagation loss is found to be less than 0.1 dBcm⁻¹ and Q-switched operation is also demonstrated. Channel waveguides are fabricated in Yb:KGd(WO₄)₂ and Yb:KY(WO₄)₂ using ultrafast laser inscription. Several of these waveguides lase in compact monolithic cavities. A maximum output power of 18.6 mW is observed, with a propagation loss of ~2 dBcm⁻¹. By using a variety of writing conditions the optimum writing pulse energy is identified. Micro-spectroscopy experiments are performed to enable a fuller understanding of the induced crystal modification. Observations include frequency shifts of Raman lines which are attributed to densification of WO₂W bonds in the crystal. Yb:tungstate lasers can generate ultrashort pulses and some preliminary work is done to investigate the use of quantum dot devices as saturable absorbers. These are shown to have reduced saturation fluence compared to quantum well devices, making them particularly suitable for future integration with Yb:tungstate waveguides for the creation of ultrafast, compact and high repetition rate lasers.