DCPHOTOPTICS 2015 Abstracts


Full Papers
Paper Nr: 1
Title:

Micromachining of Materials using Femtosecond Laser Pulses - A Parametric Study

Authors:

K. Garasz, M. Tański and J. Mizeraczyk

Abstract: In the presented research, I have undertaken the problem of femtosecond laser interactions with matter, under various laser pulse parameters and considering a wide group of materials, i.e. metals, plastics, graphene, silicon. There is a considerable interest in the precise material micro and nanomachining with ultrashort laser pulses. It is well established, that the quality of ablation process with femtosecond laser is much better than when using long pulse lasers. The use of femtosecond laser pulses creates an attractive opportunity for high quality micromachining of many groups of materials and opens an interesting field in fundamental research. The objective of the fundamental research proposed within this research is a complex study of the physical phenomena occurring during short-pulsed (femtosecond) laser interactions with matter. Although the research topic itself is very popular in the scientific community, it is relatively little elucidated. A better examination of the effects of electromagnetic irradiation on the materials in the femtosecond regime will provide a better understanding of the subject. The experimental results obtained from this project and theoretical considerations will provide a verification of the existing theories on laser-matter interactions. Additionally, the experimental investigations will be carried out on novel materials, i.e. graphene. I have specifically taken under investigation the laser ablation phenomena, which occurs during a highly energetic laser irradiation of the material and results in detachment of microparticles from the material. The physics of the ablation process in an ultrashort laser pulses regime differs from the ablation caused by the long (nanosecond and picoseconds) laser pulses. The nature of the process is more complex with the short pulses and the complete, research based understanding of the phenomena is not available yet.

Paper Nr: 2
Title:

Novel Progress in the High-sensitivity Heterolithic Ring Laser Gyroscope Technology

Authors:

R. Santagata, J. Jacopo, N. Beverini, G. Carelli, A. Di Virgilio, E. Maccioni and A. Simonelli

Abstract: The sensitivity achieved by large ring laser gyroscopes opens the perspective to observe in an Earth-located laboratory extremely small effects expected from fundamental theories of physics. The next-generation sensor that could provide the required accuracy is a multiaxial heterolithic ring laser actively stabilized via a precise external diagnostic of circulating laser beams path. Here we report about the research activities and recent progress toward the development of a large frame He-Ne triaxial sensor with an ultimate accuracy of 10^{-11}, in order to detect the relativistic Lense-Thirring effect related to the Earth rotating mass. The actual activity is focused on the control of the systematic errors related to the fluctuation of the cavity geometry and the laser active medium parameters. In this work we will discuss in details only the first issue, to which my PhD studies are mainly dedicated.

Paper Nr: 3
Title:

New Aproaches for High-Resolution Optical Microscopy

Authors:

Denis E. Trancă and George A. Stanciu

Abstract: New advances of the apertureless Scanning Near-field Optical Microscopy (a-SNOM) are presented in fields like materials science and biology. Together with experimental data, the oscillating point-dipole model (OPDM) is used for signal analysis, influence of functioning parameters analysis and for quantitative electric permittivity measurements with nanoscale resolution.

Paper Nr: 4
Title:

BAlGaN-based Vertical Cavity Surface Emitting Laser Operating in Deep UV Region

Authors:

X. LI, S. Sundaram, P. Disseix, S. Bouchoule, G. Le Gac, G. Patriarche, F. Réveret, J. Leymarie, Y. El Gmili, J. Streque, F. Genty, J-P. Salvestrini, P. L. Voss, R. D. Dupuis and A. Ougazzaden

Abstract: Vertical cavity surface emitting laser (VCSEL) is one of the most attractive configurations for semiconductor light emitting devices. However, the III-nitride VCSELs based on AlGaInN demonstrated so far operate in the wavelengths of visible violet and blue spectral range, while no efficient VCSELs operating below 300 nm were reported. To extend the VCSEL emission to the ultraviolet region, the challenges lie in many aspects, such as degradation of the structural quality of heteroepitaxial AlGaN materials with increasing Al molar ratio, lack of high quality AlN substrates, strong quantum-confined Stark effect (QCSE) induced by piezoelectric and spontaneous polarization, and decrease of TE polarization emission as the Al composition increases for the deep UV wavelength. Besides, development of high-reflectivity distributive Bragg reflector (DBR) structures with large bandwidth for the UV VCSELs is a big challenge, considering the limited refractive index contrast and large lattice mismatch for conventionally used AlGaN/Al(Ga)N structures. The objective of this work is to develop VCSELs operating below 300 nm. In this framework, the AlGaN MQWs grown on relaxed AlGaN buffer emitting at 280 nm has been studied for the active region, including AlGaN epitaxial growth for the control of composition and strain relaxation, the realization of TE-enhanced MQWs design and the related characterizations. For the DBRs, new BAlGaN material system would be applied with more freedom in bandgap, strain engineering with tailoring of refractive index. The growth conditions of BAlN single layers, BAlN/AlN heterostructure with 11% boron and structural characteristics have been explored. The promising results achieved for both AlGaN MQWs and BAlN materials advance prospects for the development of VCSELs and other light emitting devices in the DUV region.

Paper Nr: 6
Title:

Decorrelation of the Light-emitting-Diode Internal-quantum-Efficiency Components - Studies of the Electron-hole Concentration-ratio at the Active-region Edge

Authors:

Dinh Chuong Nguyen, David Vaufrey and Mathieu Leroux

Abstract: GaN-based LEDs have emerged as a very promising white-light source since the last decade and become the main part of many applications. However, such applications usually require those LEDs to operate at their high-current regime, which unfortunately sees LED internal-quantum-efficiency dropping drastically. This so-called "IQE droop" has been related to different possible causes, among those the Auger recombination and the carrier leakage have recently been nominated as the most prominent ones. The quest for the droop's main cause has raised intense debate mostly because of incomplete knowledge about the wurzite GaN and difficulties in separately evaluating the effects of the droop-inducing-mechanisms. Hence, this PhD. work aims to separately study the IQE-droop interconnected components through new approaches. Simulation and characterization have both been carried out. In this paper, simulation results at the active-region edges of two different LED structures are presented. They suggest that carrier leakage play a major role in the LED efficiency droop and lead to further p-GaN-properties studies.

Paper Nr: 7
Title:

High Power Laser Diodes with Optical Feedback - Contribution to Doctoral Consortium

Authors:

Dennis Bonsendorf

Abstract: High power direct diode lasers, as they are used in material processing or photonic pumping applications, are sensitive to back reflected light, which is usually called “optical feedback”. This feedback is generated unintendedly by optical surfaces of laser processing tools like cutting heads or by the processed surface itself. In material cutting or welding processes copper or aluminum are highly reflective materials (Steen, 2010) and photonic crystals can be origin of unwanted radiation even at changed wavelength (Dowley, 1998). Inside the laser system the beam transformation or the fiber coupling unit generates optical feedback. In some applications optical feedback is actually desired as part of the design. Volume Bragg gratings (VBG) reduce the spectral width by utilization of feedback. However, there is a price to pay, when the reflected light reaches the emitter of the laser diodes it can result in spectral modulation, lifetime reduction or catastrophic optical (mirror) damage (COMD).

Paper Nr: 8
Title:

Concepts and Design of Novel Integrated Photonic Devices based on Silicon-organic Hybrid Technology

Authors:

Patrick Steglich, Mauro Casalboni and Sigurd Schrader

Abstract: n/a

Paper Nr: 9
Title:

An Explanation of the Physical Origin of the Extra-ordinary Angular Tolerance of Cavity Resonator Integrated Grating Filters

Authors:

Nadège Rassem, Anne-Laure Fehrembach and Evgeni Popov

Abstract: Cavity – resonator - integrated guided - mode resonance filters (CRIGFs) are promising structures that afford a very fine spectral width less than 1 nm. We study another structure to compare compare it to CRIGF. The angular acceptance of CRIGF is an order of magnitude greater than in classical gratings, even with complex pattern. To identify the phenomenon responsible for the extraordinary large angular acceptance of CRIGF, we study the dispersion curve of the mode excited in the CRIGF.

Paper Nr: 10
Title:

Integrated Fibre Optics for Sensing based on Whispering-Gallery Modes

Authors:

Yazmin Padilla Michel, Sigurd Schrader, Mauro Casalboni and Patrick Steglich

Abstract: WGMs in MMF have a double impact in the performance of finished devices. On one hand, the oscillatory effect on the spectrum has been an undesirable instrument footprint, for applications where a flat and stable reference spectrum is required (e.g. Astrophysics, Medicine or Pharmacy). On the other hand, with this thesis we want to prove that the WGM produced in MMF can be the base for a potential low-cost and profitable resonator. This will be achieved exploiting the helicoidal modes propagating along the coating of MMF, which resemble the WGM observed in the spectrum of a coil resonator. The present thesis project has two main objectives. First objective is to provide a solution to the so-called“fringing-like pattern” observed for example in fibre bundles made with circular-core MMF (Lagerholm, et al 2012). The second objective is to develop an innovative, efficient and profitable resonator, exploiting the WGM produced in MMF. All these results will be very useful for a better understanding of mode behaviour in MMF.

Paper Nr: 11
Title:

Silicon Kerr Effect Electro-optic Switch

Authors:

Deepak V. Simili and Michael Cada

Abstract: Design of an ultrafast silicon electro-optic switch is presented. Silicon nanocrystals in silica is chosen as the optical medium and the ultrafast Kerr effect is utilized. A preliminary analysis of the performance parameters for the switch with the chosen ring resonator structure is discussed. Theoretical calculation of the maximum modulation bandwidth is obtained to be 137.409 GHz.

Paper Nr: 13
Title:

Mode-locked Thulium-Doped Fiber Lasers based on Highly Ge-doped Fibers

Authors:

Dmitry Klimentov, V. V. Dvoyrin and I. T. Sorokina

Abstract: We report and compare three configurations of the SESAM mode-locked, linear cavity femtosecond all-fiber MOPA based on a highly Ge-doped Thulium-doped normal dispersion fibers. We have studied the performance of the system and have obtained stable mode-locking in a wide cavity dispersion range at around 1.88 μm. In this article we focus our attention on three particular configurations: laser operating in the anomalous, nearly zero and normal cavity dispersion regimes without the use of the additional dispersion compensating elements. For the nearly zero and normal cavity dispersion regimes the femtosecond pulses with several nanojoule energy were obtained. The pulses were compressed down to 800 fs using a simple fiber compressor represented by a piece of the conventional telecommunication fiber.