Radan Slavík

Novel spectral fiber optic sensor based on surface plasmon resonance

Abstract A novel fiber optic surface plasmon resonance (SPR) sensing device based on spectral interrogation of SPR in a miniature fiber optic sensing element using depolarized light is reported. Optimization analysis of the sensor based on the equivalent planar waveguide approach and the mode expansion and propagation method is presented. A laboratory prototype of the sensor has been proved to be able to measure refractive index variations as small as 5×10−7. Suitability of the sensor for biosensing has been demonstrated by detecting IgG via respective monoclonal antibodies immobilized on the SPR sensor surface.

A miniature fiber optic surface plasmon resonance sensor for fast detection of Staphylococcal enterotoxin B.

A fiber optic surface plasmon resonance (SPR) biosensor for detection of Staphylococcal enterotoxin B (SEB) is reported. The sensor is based on spectral interrogation of surface plasmons in a miniature sensing element based on a side-polished single-mode optical fiber with a thin metal overlayer. For specific detection of SEB, the SPR sensor is functionalized with a covalently crosslinked double-layer of antibodies against SEB. The SPR biosensor is demonstrated to be able to detect ng/ml concentrations of SEB in less than 10 min.

Single-mode optical fiber surface plasmon resonance sensor

Abstract A fiber optic surface plasmon resonance (SPR) sensor utilizing the resonant interaction between a guided mode of a single-mode optical fiber and a surface plasma wave supported by a thin metal film is described. Theoretical analysis of the SPR sensing structure based on the equivalent planar waveguide approach and the mode expansion and propagation method is presented. A detailed analysis of the effect of the major parameters of the SPR sensing structure on the sensor performance is carried out. Experimental results obtained with fabricated laboratory prototypes of the SPR sensing device for measurement of the refractive index of analyte are reported. It has been demonstrated that the fiber optic SPR sensing device may be used as a spectral as well as an amplitude sensor.

Miniaturization of fiber optic surface plasmon resonance sensor

Abstract A novel design of surface plasmon resonance (SPR) sensor is reported which leads to a highly miniaturized optical fiber sensing element with high sensitivity. A surface plasmon wave is excited on a thin metal film on a side-polished single-mode optical fiber and variations in the refractive index of analyte are detected by measuring changes in the intensity of the light back-reflected from a mirrored end face of the fiber. The operation range of the sensor is tuned toward aqueous media by using a thin tantalum pentoxide overlayer. It is demonstrated that the sensor is capable of detecting changes in the refractive index below 4×10 −5 .

High-resolution microwave frequency transfer over an 86-km-long optical fiber network using a mode-locked laser

We demonstrate the transfer of an ultrastable microwave frequency by transmitting a 30-nm-wide optical frequency comb from a mode-locked laser over 86 km of installed optical fiber. The pulse train is returned to the transmitter via the same fiber for compensation of environmentally induced optical path length changes. The fractional transfer stability measured at the remote end reaches 4×10(-17) after 1600 s, corresponding to a timing jitter of 64 fs.

First demonstration of all-optical QPSK signal regeneration in a novel multi-format phase sensitive amplifier

We propose a novel black-box optical phase sensitive amplifier (PSA) configuration and describe its application to the regeneration of multi-level phase encoded signals. The concept is demonstrated with a 10 Gbaud quadrature phase shift keyed (QPSK) input.

Demonstration of amplified data transmission at 2 µm in a low-loss wide bandwidth hollow core photonic bandgap fiber

The first demonstration of a hollow core photonic bandgap fiber (HC-PBGF) suitable for high-rate data transmission in the 2 µm waveband is presented. The fiber has a record low loss for this wavelength region (4.5 dB/km at 1980 nm) and a >150 nm wide surface-mode-free transmission window at the center of the bandgap. Detailed analysis of the optical modes and their propagation along the fiber, carried out using a time-of-flight technique in conjunction with spatially and spectrally resolved (S2) imaging, provides clear evidence that the HC-PBGF can be operated as quasi-single mode even though it supports up to four mode groups. Through the use of a custom built Thulium doped fiber amplifier with gain bandwidth closely matched to the fibers low loss window, error-free 8 Gbit/s transmission in an optically amplified data channel at 2008 nm over 290 m of 19 cell HC-PBGF is reported.

Advanced biosensing using simultaneous excitation of short and long range surface plasmons

We present a novel optical biosensor which exploits simultaneous excitation of two different surface plasmons in a single sensing spot. It allows compensation of cross-sensitivity to background refractive index change, as a typical surface plasmon resonance sensor is sensitive to both the absorption of a thin film on the surface (sensing event) and the refractive index change of the background (an interfering effect). The structure parameters are optimized to yield low noise and minimum cross-sensitivity. In the performed model experiment, IgE biomolecules at a concentration of 250 ng ml−1 are detected during a change in the background refractive index of 10−3.

Generation of customized ultrahigh repetition rate pulse sequences using superimposed fiber Bragg gratings

We propose and experimentally demonstrate the use of superimposed fiber Bragg gratings (FBGs) as amplitude or phase filtering stages for generating ultrahigh-repetition-rate optical pulse bursts from a single ultrashort pulse. This approach offers the advantages of a compact all-fiber solution and provides high flexibility in tailoring the temporal features of the generated pulse sequence, namely, the repetition rate, as well as the shape and duration of both the individual pulses and the temporal envelope of the burst. To demonstrate the capabilities of the proposed approach, we generate near-flat-topped optical pulse bursts with repetition rates as high as /spl ap/170 GHz at a wavelength of 1.55 /spl mu/m using uniform and linearly chirped superimposed FBGs. We show that superimposed linearly chirped FBGs are more energetically efficient and provide increased design flexibility than superimposed uniform FBGs. Our experimental results also show the robustness of the technique to imperfections in the grating structures and to variations in the input pulse quality.

Terahertz-bandwidth high-order temporal differentiators based on phase-shifted long-period fiber gratings

We report the fabrication of a pi-phase-shifted long-period fiber grating (LPFG) capable of operating as a terahertz-bandwidth second-order temporal differentiator. We demonstrate its operation experimentally by differentiating subpicosecond long optical pulses. A new scheme for achieving high-order photonic temporal differentiation based on LPFG filters is also proposed and demonstrated. In particular, we prepared a LPFG-based first-order differentiator that was frequency and bandwidth matched to the second-order device and demonstrated the cascadability of these devices leading to the implementation of a third-order differentiator. By also employing these devices in reflection, up to the fifth-order differentiation is demonstrated experimentally.