Arrayed-waveguide-grating light collector for on-chip spectroscopy

We present a novel arrayed-waveguide-grating (AWG) device with improved external (biomedical) signal collection for use in on-chip spectroscopy. The collection efficiency of the device is compared to that of a standard AWG. We also present experimental results on the collection efficiency and size of the collection volume

Towards spectral-domain optical coherence tomography on a silicon chip

Optical coherence tomography (OCT) is a widely used optical imaging technology, particularly in the medical field, since it can provide non-invasive, sub-micrometer resolution diagnostic images of tissue. Current OCT systems contain optical fibers and free-space optical components which make these instruments bulky and costly. A significant decrease in the size and cost of an OCT system is possible through the use of integrated optics, allowing for compact and low-cost OCT systems, especially suited for applications in which instrument size may play an important role. In this work, we present a miniaturized spectral-domain OCT (SD-OCT) system. We design an arrayed waveguide grating (AWG) spectrometer in silicon oxynitride for the 1300-nm spectral range. The spectral range of the SD-OCT system near 1300 nm is specifically selected for skin imaging. We aim at 18-μm depth resolution (determined by the full width at half maximum values of the transmission spectrum of the AWG) and a 1-mm depth range (determined by the wavelength spacing per output waveguide). The free spectral range of 78 nm and wavelength resolution of 0.4 nm of the AWG are determined to meet these requirements. We use ahe fiber-based SD-OCT system with AWG spectrometer. The Michelson interferometer is illuminated using a superluminescent diode which has a Gaussian-like spectrum with a bandwidth of 40 nm and a central wavelength of 1300 nm. Via a circulator the light is coupled into a 90/10 beamsplitter. Polarization controllers are placed into both, sample and reference arm. The backreflected light is redirected through the optical circulator to the AWG spectrometer. The collimated beam is imaged with a camera lens onto a 46 kHz CCD linescan camera. The acquired spectra are processed by first subtracting the reference arm spectrum, then compensating the dispersion, and finally resampling to k-space. We achieve a depth range of 1mm. The measured signal-to-noise ratio (SNR) is 75 dB. The axial resolution (FWHM) is determined from a Gaussian fit to the point spread function in amplitude at various depths. A slight decrease in depth resolution is observed at higher depth ranges, which we attribute to misalignment and lens aberrations. As a demonstration of OCT imaging using the AWG spectrometer, an image of a layered phantom is recorded. The phantom consists of three layers of scattering medium (µs = 4 mm-1, refractive index n = 1.41) interleaved with non-scattering tape. We can observe all three scattering layers up to the maximum imaging depth of 1 mm

Raman spectroscopy and optical coherence tomography on a micro-chip

We review our recent results on integrating biomedical optical systems onto a silicon chip

Dynamic mechanical analysis of suspended soft bodies via hydraulic force spectroscopy

© 2023 The Royal Society of Chemistry.The rheological characterization of soft suspended bodies, such as cells, organoids, or synthetic microstructures, is particularly challenging, even with state-of-the-art methods (e.g. atomic force microscopy, AFM). Providing well-defined boundary conditions for modeling typically requires fixating the sample on a substrate, which is a delicate and time-consuming procedure. Moreover, it needs to be tuned for each chemistry and geometry. Here, we validate a novel technique, called hydraulic force spectroscopy (HFS), against AFM dynamic indentation taken as the gold standard. Combining experimental data with finite element modeling, we show that HFS gives results comparable to AFM microrheology over multiple decades, while obviating any sample preparation requirements

Linear electro-optic coefficient in multilayer self-organized InAs quantum dot structures

The electro-optic coefficients of self-organized InAs quantum dot layers in molecular beam epitaxy grown laser structures in reverse bias have been investigated. Enhanced electrooptic coefficients compared to bulk GaAs were observed. © 2003 Optical Society of America

Observation of sound-induced corneal vibrational modes by optical coherence tomography

7 págs.; 7 figs.; OCIS codes: (170.4500) Optical coherence tomography; (170.4470) Ophthalmology; (100.3010) Image reconstruction techniques.The mechanical stability of the cornea is critical for maintaining its normal shape and refractive function. Here, we report an observation of the mechanical resonance modes of the cornea excited by sound waves and detected by using phase-sensitive optical coherence tomography. The cornea in bovine eye globes exhibited three resonance modes in a frequency range of 50-400 Hz. The vibration amplitude of the fundamental mode at 80-120 Hz was ~8 μm at a sound pressure level of 100 dB (2 Pa). Vibrography allows the visualization of the radially symmetric profiles of the resonance modes. A dynamic finite-element analysis supports our observation. ©2015 Optical Society of AmericaThis work was supported by National Institutes of Health (R01-EY025454, P41-EB015903, UL1-RR025758, R21EY023043, K25EB015885), National Science Foundation (1264356), European Research Council (ERC-2011 AdG-294099), and Spanish Government (FIS2011- 25637; FIS2014-56643-R and FPI-BES-2009-024560).Peer Reviewe

High-resolution integrated spectrometers in silicon-oxynitride

Arrayed waveguide grating spectrometers operating around 800 nm and 1300 nm are demonstrated, with the highest resolution (0.16 nm) and largest free spectral range (77 nm) achieved in silicon-oxynitride technology to date

Miniature spectrometer and beam splitter for an integrated optical coherence tomography system

In this paper we present an important step toward a cheap, compact, and quasi-maintenance-free spectral-domain OCT system by integrating its central components, the beam splitter and spectrometer, on a silicon chip

Biophotonic sensors on a microchip for trace-gas detection, DNA and enzyme analysis, Raman spectroscopy, and optical coherence tomography

Use of optical principles for the detection and analysis of biomolecules and biotissue has a long-standing tradition, and highly sensitive optical methods have been developed. Integration on a microchip offers cost reduction and instrument miniaturization, thus enabling novel applications, but also allows reduced biosample volumes, higher sensitivity, and faster acquisition times. We demonstrate optical sensing with Bragg-grating cavities inscribed into optical waveguides for label-free sensing of antibody-antigen protein reactions and H2 gas sensing by stress-induced Pd-receptor microcantilever deflections. Furthermore, we introduce the method of modulation-frequency-encoded multi-wavelength fluorescent DNA analysis in an optofluidic chip during capillary electrophoresis separation, enabling detection down to the single-molecule level and allowing simultaneous analysis of DNA fragments from independent human genomic segments, associated with genetic predispositions to breast cancer and anemia, in a single experiment. Finally, by integrating wavelength-selective arrayed-waveguide gratings on a microchip, we demonstrate on-chip Raman spectroscopy and spectral-domain optical coherence tomography of biotissue