Jiri Ctyroky

Novel surface plasmon resonance sensor based on single-mode optical fiber

Surface plasmon resonance sensor based on resonant interaction between a guided mode of a single-mode optical fiber and a surface plasmon wave supported by a thin metal overlayer is presented. Two modes of operation of the sensor based on the measurement of changes in the fiber mode attenuation and on the measurement of changes in the wavelength at which the resonance occurs are described. Theoretical analysis of the proposed sensing structure based on the equivalent planar waveguide approach and the mode expansion and propagation method is carried out. It is shown that the operation range of the sensor may be tuned by a thin dielectric overlayer. Experimental results have shown that in both the modes of operation the sensor is capable of detecting changes in the refractive index of the sensed medium below 2 multiplied by 10-5.

Efficient Boundary Conditions for Bidirectional Propagation Algorithm Based on Fourier Series

Recently, we described a very simple but efficient bidirectional eigenmode expansion propagation algorithm based on Fourier series expansion for modeling optical field distribution in waveguide devices. In this communication, we report on the implementation of complex coordinate transformation into this algorithm as absorbing boundary conditions that greatly enhance the suppression of unwanted reflections from the boundaries of the computational window.

Novel approach to surface plasmon resonance multichannel sensing

We present a novel surface plasmon resonance (SPR) sensor based on serial organization of sensing channels and sequential spectral encoding of responses from sensing channels into an optical spectrum. This approach allows probing interfacial processes by surface plasmons of different field profiles which makes it possible to distinguish surface and bulk contributions to SPR sensor response. We illustrate this unique feature of the presented approach in a model biosensing experiment in which the detection of human chorigonadotropin (hCG) is compensated for background refractive index interference.

Separation of refractive index and temperature measurements using surface plasmon-coupled fiber grating

A new fiber optic sensor based on Bragg reflection influenced by a surface plasmon is presented. This arrangement allows for self-referencing due to its highly polarization-resolved response.

Advances in development of miniature fiber optic surface plasmon resonance sensors

We present an optical sensor based on excitation of surface plasma waves in optical fiber structure consisting of a side-polished single-mode polarization-maintaining fiber and a metal overlayer. We describe two modes of operation of the sensor in which variations in the refractive index of the sample are determined by measuring changes in the transmitted optical power at a fixed wavelength (amplitude mode) and by measuring changes in the wavelength at which the resonant attenuation of the fiber mode occurs (spectral mode). We demonstrate that this design allows suppressing sensitivity of the sensor to deformation of the fiber yielding an improved stability and resolution.

Miniature fiber optic surface plasmon resonance biosensors

A novel design of surface plasmon resonance fiber optic sensor is reported which leads to a compact, highly miniaturized sensing element with excellent sensitivity. The sensing device is based on a side-polished single-mode optical fiber with a thin metal overlayer supporting surface plasmon waves. The strength of interaction between a fiber mode and a surface plasmon wave depends strongly on the refractive index near the sensing surface. Therefore, refractive index changes associated with biospecific interaction between antibodies immobilized on the sensor and antigen molecules can be monitored by measuring light intensity variations. Detection of horse radish peroxidase (HRP) of the concentration of 100 ng/ml has been accomplished using the fiber optic sensor with a matrix of monoclonal antibodies against HRP immobilized on the sensor surface.

Light Advancement and Delay by Linear Filters With Close to Zero Resonant Transmittance

Filters operated close to the critical coupling were reported to be capable of an increase and decrease of the group velocity. The published examples are ring resonators (feedback-based filter) and Mach-Zehnder filters (no feedback filters). Here we show that these linear filters have, within certain bandwidth, identical filtering characteristics, although they are based on completely different filtering principles. Further, we demonstrate experimentally a long period fiber grating as another no-feedback filter that is capable to perform similar filtering characteristics when operated close to the critical coupling condition. This scheme may be of interest due to inherently large bandwidth provided by long-period fiber grating based filters. In the example given here, filters compatible with systems operating at repetition rates up to 40 GHz are demonstrated.

Exchangeable grating couplers for integrated optics

Mode spectroscopy is a widely used technique for characterizing planar optical waveguides. Prism couplers are mostly used due to their versatility. For higher-index waveguides like SiO2/SiN or GaInAsP/InP, prism coupling is hampered by the lack of suitable high-index material for fabricating coupling prisms. In this case, short-period grating couplers could be used, instead. We describe the fabrication of “exchangeable” grating couplers with 1200, 1800, and 2400 lines/mm into a photo-curable polymer by copying master grating generated holographically. The grating couplers were applied to glass and Si/SiO2/SiN waveguides, and results were compared with those obtained using prism coupling. Fabrication of gratings with shorter periods is under way.

Fiber optic surface plasmon resonance sensor with a Bragg grating

We report a new optical sensor based on excitation of a surface plasmon in an optical fiber Bragg grating (FBG) structure. The sensing device consists of a side-polished single-mode optical fiber with a Bragg grating written into a fiber core and a thin gold overlayer supporting SP. If a coupling between a guided mode of the optical fiber and a SP mode is established, any change in the refractive index of analyte affects propagation constant of the fiber mode producing a change in the amount of light reflected by the FBG. A laboratory prototype of the sensor has been developed and its potential for refractometry has been examined. It has been demonstrated that the sensors sensitivity to refractive index is as high as 750 dB/RIU.

Surface plasmon resonance sensors using optical waveguides

Optical waveguide surface plasmon resonance (SPR) sensors are presented which exploit the phenomenon of the resonant excitation of surface plasmon waves by guided modes of optical fibers and integrated optical waveguides. Theoretical analysis of the SPR waveguide sensing structures is based on the mode expansion and propagation method. The integrated optical waveguide SPR sensor is composed of an optical waveguide fabricated by the K+--Na+ ion exchange in a glass substrate and gold as a surface plasmon resonance overlayer. The optical fiber SPR sensor is realized on a side-polished single-mode optical fiber which is locally coated with a thin gold film. Experimental study of the realized samples of the sensors has shown that variations in the refractive index of the sensed medium below 5X10-5 can be resolved with the sensors.