Phase shifted microcavities

Chat with Graph Search

Ask any question about EPFL courses, lectures, exercises, research, news, etc. or try the example questions below.

DISCLAIMER: The Graph Chatbot is not programmed to provide explicit or categorical answers to your questions. Rather, it transforms your questions into API requests that are distributed across the various IT services officially administered by EPFL. Its purpose is solely to collect and recommend relevant references to content that you can explore to help you answer your questions.

Non-ablative femtosecond laser processing of transparent substrates involves cumulative, multi-timescale dynamics that hinder precise control of induced structural modifications. Here, we demonstrate a feedback-compatible diagnostic based on mid-infrared transmission monitoring using a continuous-wave QCL emitting at 4.46 µm. This approach enables in situ observation of structural dynamics induced by femtosecond laser irradiation at repetition rates up to 250 kHz. The technique shows sensitivity to key tran

Wavelength‐tunable pulsed lasers have garnered significant research interest due to their critical role in applications requiring precise spectral matching, such as wavelength‐division multiplexing and spectroscopic analysis. Although recent hybrid architectures integrating saturable absorbers with wavelength‐selective components have enabled notable progress, these systems remain constrained by two fundamental challenges: excessive coupling losses and complex alignment procedures. Here, a compact wavelengt

Diffusion models generate new samples by progressively decreasing the noise from the initially provided random distribution. This inference procedure generally utilizes a trained neural network numerous times to obtain the final output, creating significant latency and energy consumption on digital electronic hardware such as GPUs. In this study, we demonstrate that the propagation of a light beam through a semi-transparent medium can be programmed to implement a denoising diffusion model on image samples.

Self-pulsating lasers based on cascaded reshaping and reamplification (2R) are capable of initiating ultrashort pulses despite the accumulation of large amounts of nonlinearities in all-fiber resonators. The spectral properties of pulses in self-similar propagation are compatible with cascaded 2R regeneration by offset filtering, making parabolic pulses suitable for the design of a laser of this recently introduced class. A new type of regenerative laser giving birth to similaritons is numerically investiga

We propose a device architecture capable of direct quantum coherent electro-optical conversion of microwave-to-optical photons. The hybrid system consists of a planar superconducting microwave circuit coupled to an integrated whispering-gallery-mode microresonator made from an electro-optical material. We show that by exploiting the large vacuum electric field of the planar microwave resonator, electro-optical (vacuum) coupling strengths g(0) as large as similar to 2 pi O(10 - 100) kHz are achievable with c

Due to their fascinating optical and electronical properties, nanometer-scaled structures play an important role in solar energy conversion [1]. Nanocomposite coatings consist typically of dielectric, semiconducting or metallic nanocrystals embedded in a host matrix. In this presentation it will be described how such nanostructures can result in interesting new material properties which might be exploited in solar energy conversion. This overview tries to illustrate the large variety of existing and envisag

Many biological objects are mainly transparent and weakly scattering, thus a promising (and already widely used) way of imaging them consists in considering optical refractive index variations. The method proposed here permits 3D imaging of the refractive index distribution with a tomographic approach. Usually, the classical Radon transform does not sufficiently take into account the physical interaction between light and biological cells, therefore diffraction has to be considered.

Using tunnel junction patterning and double wafer fusion, we demonstrate phase-locked arrays of VCSELs emitting at the 1300 nm waveband. CW powers as high as 10 mW and coherent beams are demonstrated for various array configurations. (C) 2009 Optical Society of America

We present a novel Fourier domain method for microscopic imaging - so- called k-microscopy - with lateral resolution independent of the detection numerical aperture. The concept is based on sample illumination by a lateral fringe- pattern of varying spatial frequency, which probes the lateral spatial frequency or k- spectrum of the sample structure. The illumination pattern is realized by interference of two collimated coherent beams. Wavelength tuning is employed for modulation of the fringe spacing. The u

Digital holographic microscopy (DHM) is a technique that allows obtaining, from a single recorded hologram, quantitative phase image of living cell with interferometric accuracy. Specifically, the optical phase shift induced by the specimen on the transmitted wave front can be regarded as a powerful endogenous contrast agent, depending on both the thickness and the refractive index of the sample. We discuss some approaches allowing to directly obtain separate measurements of the thickness and the refractive

We report a novel three-contact vertical-cavity surface-emitting laser (VCSEL) for use in polarization-sensitive optical applications. The device consists of two vertical cavities, coupled by a common mirror. We demonstrate that one can independently choose both the power of the output beam-through the current in the first cavity-and the polarization state-through the bias applied to the second cavity. The control of the polarization state is performed with a control voltage in the range -2 to 0 V. Within t

We report direct absorption spectroscopic detection of ozone at ambient pressure with a pulsed, DFB quantum-cascade laser (QCL) tuned within 1044-1050 cm(-1) by temperature scanning. Wavelength calibration curves were derived from FTIR and CO2 spectra and interpreted with respect to the heat transfer from the heterostructure to the sink. The laser linewidth (similar to0.13 cm(-1) FWHM) was found to decrease with temperature, probably as a result of operation at constant current. Spurious spectral features d

Over the past decade a new family of optoelectronic devices has emerged whose performance is enhanced by placing the active device structure inside a Fabry–Perot resonantmicrocavity [P. E. Green, IEEE Spectrum 13 (2002)]. The increased optical field allows photodetectors to be made thinner and therefore faster, while simultaneously increasing the quantum efficiency at the resonant wavelengths. We have demonstrated a variety of resonant cavity enhanced (RCE) photodetectors in compound semiconductors [B. Yang

Doping of organic light-emitting devices using highly luminescent molecules is a well-established strategy to improve brightness, efficiency and lifetime or to adjust emission color and color purity. Laser dyes from the pyran-containing donor-acceptor family are particularly interesting for emission in the yellow and red spectral domain. In solution, these polar dyes show marked solvatochromic shifts in the absorption and emission. The fluorescence quantum efficiency also depends strongly on solvent polarit

We report on the growth by metalorganic vapor phase epitaxy of a InGaN/GaN resonant-cavity light emitting diode (RCLED) emitting at 454 nm and incorporating a 12-pair Al0.82In0.18N/GaN distributed Bragg reflector as bottom mirror. A(1-x)In(x)N layers with an Al content around x similar to 0.17 are lattice matched to GaN, thus avoiding strain-related issues in the subsequent active layers while keeping a high refractive index contrast of 7%, comparable to that achievable in the Al0.5Ga0.5N/GaN system. Device

We present a study on the improvement of the external Quantum Efficiency (QE) of Gallium-Nitride-based Light Emitting Diodes (LEDs) by the use of the Single Mirror (SMLED) design [N.E.J. Hunt et al., Electron. Lett. 28, 2169 (1992)]. Three different substrate emitting LEDs are compared by measurements and simulations. An increase in the external QE by more than a factor of two is demonstrated, due to the enhancement of the Light Extraction Efficiency for the SMLED design. Using the SMLED design leads to val

The present work investigates the possibility of selective electrochemical metal deposition on ion implanted p-Si. The idea is that defects introduced into the substrate by ion implantation make it more susceptible to electrochemical reactions compared to intact Si; this increased sensitivity is to be used for selective reactions at the defect sites. It is believed that the increased reactivity is due to a lowering of the Schottky barrier breakdown potential, Ubd, of the semiconductor-electrolyte interface

The fluctuating behaviour of a Sulzer Metco F4 DC plasma gun has been investigated. The time dependencies of the arc voltage and current and of the optical emission of the plasma jet have been measured. An optical fibre inside the gun allows direct measurement of optical fluctuations of the arc. Spectral and statistical analysis of the recorded signals are, presented for various working gas mixtures and for two types of gas injection. There is a dominant fluctuation frequency around 4 kHz which appears to b

We present a tunable interference filter for infrared and visible light that scans the desired part of the optical spectrum within milliseconds. A single pixel detector measures serially the intensity at selected wavelengths. This concept avoids expensive linear detectors as used for grating spectrometers. The tunable optical interference filter is fabricated by a new porous silicon batch technology using only two photolithography steps. The refractive index of this filter microplate is gradually modulated

Chalcogenide glass optical fibers were fabricated into functional apertured probes for near field scanning infrared microscopy. Probe fiber tips were chemically etched and aluminum coated for the purpose of simultaneously collecting near field shear force and optical signals. Surface topography and infrared optical reflectivity data were obtained using the tips in a scanning near field microscope while illuminating an integrated microcircuit with the output from a free electron laser operating at a lambda o

Phase shifted microcavities

Chat with Graph Search

Laser-based in situ monitoring of femtosecond-laser in-bulk processing of glass

Wavelength Tunable Pulsed Lasers Enabled by a Versatile Metafiber Functioning as Both Saturable Absorber and Filter

Optical Computing for Machine Learning with Integrated Waveguides

Regenerative similariton laser

On-chip microwave-to-optical quantum coherent converter based on a superconducting resonator coupled to an electro-optic microresonator

Nanocomposite Coatings for Solar Energy Conversion: Large Opportunities for Small Structures

Diffraction tomography for biological cells imaging using digital holographic microscopy

1.3-mu m Wavelength Coupled VCSEL Arrays Employing Patterned Tunnel Junction

k-Microscopy: resolution beyond the diffraction limit

Analysis of cellular structure and dynamics with digital holographic microscopy

Control of polarization switching in vertical coupled-cavities surface emitting lasers

Ozone detection by differential absorption spectroscopy at ambient pressure with a 9.6 mu m pulsed quantum-cascade laser

High-speed Si resonant cavity enhanced photodetectors and arrays

Space charge and polarization effects upon doping organic light-emitting diodes with pyran-containing donor-acceptor molecules

InGaN/GaN resonant-cavity LED including an AlInN/GaN bragg mirror

GaN-based Single Mirror Light Emitting Diodes with high external quantum efficiency

Electrochemical investigation of ion implanted p-Si

Characterisation and origin of arc fluctuations in a F4 DC plasma torch used for thermal spraying

Microspectrometer based on a tunable optical filter of porous silicon

Scanning near field infrared microscopy using chalcogenide fiber tips