Polarimetric optical-fibre sensor for biochemical measurements

The use of an optical-fibre polarimeter as a chemical sensor is demonstrated. The compound to be detected is allowed to adsorb onto a decladded 5 cm length of the fibre. The fibre is polarization maintaining with an elliptical fibre core and a D-shaped geometry. The overall retardation stability of this fibre polarimeter is ≈ 0.5 × 2π rad m−1 K−1. With this sensor adsorption processes of proteins can be followed on-line. The resulting relative phase retardations caused by the growth of a monolayer of antibodies (αhCG, αhSA) are 0.25 × 2π. For the much smaller protein hSA, this value is 0.1 × 2

Realization and Characterization of a Four-Channel Integrated Optical Young Interferometer

In this paper, we report the realization and characterization of a four-channel integrated optical Young interferometer (YI), which enables simultaneous and independent monitoring of three binding processes. The simultaneous and independent measurement of three different glucose concentrations shows the multi-purpose feature of such device. The phase resolution for different pairs of channels was /spl sim/1/spl times/10/sup -4/ fringes, which corresponds to a refractive index resolution of /spl sim/8.5/spl times/10/sup -8/ . The observed errors, which are caused due to mismatching of spatial frequencies of individual interference patterns with those determined from the CCD camera, have been reduced by using different reduction schemes. In addition, we have investigated a novel method for discrimination of the refractive index change from the thickness of a bound layer during an immunoreaction, as well as measuring the temperature change the takes place during such a process

On-chip Mach-Zehnder interferometer for OCT systems

By using integrated optics, it is possible to reduce the size and cost of a bulky optical coherence tomography (OCT) system. One of the OCT components that can be implemented on-chip is the interferometer. In this work, we present the design and characterization of a Mach-Zehnder interferometer consisting of the wavelength-independent splitters and an on-chip reference arm. The Si3N4 was chosen as the material platform as it can provide low losses while keeping the device size small. The device was characterized by using a home-built swept source OCT system. A sensitivity value of 83 dB, an axial resolution of 15.2 μm (in air) and a depth range of 2.5 mm (in air) were all obtained

Drift correction in a multichannel integrated optical young interferometer

We demonstrate that in a sensor based on a multichannel Young interferometer, the phase information obtained for different pairs of channels can be used to correct the long-term instability (drift) due to temperature differences between measuring and reference channels, the drift in the alignment of the setup, etc. Experiments show that the nature of a major part of the drift is such that the drift present in one of the channels can be determined by interpolation of the drift measured in the two adjacent channels. It is shown that a drift reduction of 10 times can be achieved as compared with the situation in which no correction is applied. We anticipate that these findings will permit the exploitation of the extreme sensitivity of interference-based sensors to a much greater extent

Decreasing the Size of a Spectral Domain Optical Coherence Tomography System with Cascaded Arrayed Waveguide Gratings in a Photonic Integrated Circuit

This paper describes a proof-of-concept of a miniaturized spectral-domain optical coherence tomography system, based on photonic integrated circuit (PIC) technology. The integrated optics 512-channel spectrometer consists of cascaded arrayed waveguide gratings (AWG) with the output waveguides directly attached to a CCD detector. The spectrometer has a center wavelength of 850 nm and a spectral sampling interval of 0.22 nm. The PIC has a footprint of 2.0 × 2.7 cm2. The wavelength response of the cascaded AWG spectrometer is calibrated with a tunable laser. Free space OCT measurements are done with a mirror as sample. The signal-to-noise ratio is ∼77 dB. Due to the ∼three times larger optical bandwidth incident on each CCD pixel, the sensitivity rolls off faster in depth than based on the spectral sampling interval. The axial resolution of the OCT system is determined at 5.9 ± 0.4 μm. We demonstrate the imaging capabilities of this PIC based system by imaging a multilayered phantom. Our results show the basis for the development of a handheld OCT system based on PIC technology, thereby facilitating the development of more applications of OCT