Igor Shavrin

Gas refractometry using a hollow-core photonic bandgap fiber in a Mach-Zehnder-type interferometer

We present the design of a fiber-optic gas refractometer that enables spectrally resolved measurements of both real and imaginary parts of the complex refractive index. The proposed concept is based on a Mach-Zehnder-type interferometer with a hollow-core photonic bandgap fiber in one of the interferometer’s arms. The fiber is used simultaneously as an optical waveguide and an analyte containing cell. We demonstrate the performance of the device by measuring the complete complex refractive index of an air-acetylene gas mixture within the optical C-band. The introduced concept leads towards versatile applications in optics as well as atomic and molecular physics.

Numerical solver for supercontinuum generation in multimode optical fibers

We present an approach for numerically solving the multimode generalized nonlinear Schrödinger equation (MM-GNLSE). We propose to transform the MM-GNLSE to a system of first-order ordinary differential equations (ODEs) that can then be solved using readily available ODE solvers, thus making modeling of pulse propagation in multimode fibers easier. The solver is verified for the simplest multimode case in which only the two orthogonal polarization states in a non-birefringent microstructured optical fiber are involved. Also, the nonlinear dynamics of the degree and state of spectral polarization are presented for this case.

Mode excitation and supercontinuum generation in a few-mode suspended-core fiber

We have studied the excitation of higher-order modes and their role in supercontinuum generation in a three-hole silica suspended-core fiber, both experimentally and numerically. We find that pump coupling optimized to highest transmission can yield substantial excitation of higher order modes. With up to about 40% of the pump power coupled to higher order modes, we have studied supercontinuum generation in this fiber. In agreement with experiments, simulation results based on the multimode generalized nonlinear Schrödinger equation confirm that the spectral width is determined by spectral broadening in the fundamental mode, whereas the numerical analysis reveals that intermodal nonlinear interactions are strongly suppressed.

Stroboscopic white-light interferometry of vibrating microstructures

We describe a LED-based stroboscopic white-light interferometer and a data analysis method that allow mapping out-of-plane surface vibration fields in electrically excited microstructures with sub-nm amplitude resolution for vibration frequencies ranging up to tens of MHz. The data analysis, which is performed entirely in the frequency domain, makes use of the high resolution available in the measured interferometric phase data. For demonstration, we image the surface vibration fields in a square-plate silicon MEMS resonator for three vibration modes ranging in frequency between 3 and 14 MHz. The minimum detectable vibration amplitude in this case was less than 100 pm.

Picosecond supercontinuum light source for stroboscopic white-light interferometry with freely adjustable pulse repetition rate

We present a picosecond supercontinuum light source designed for stroboscopic white-light interferometry. This source offers a potential for high-resolution characterization of vibrational fields in electromechanical components with frequencies up to the GHz range. The light source concept combines a gain-switched laser diode, the output of which is amplified in a two-stage fiber amplifier, with supercontinuum generation in a microstructured optical fiber. Implemented in our white-light interferometer setup, optical pulses with optimized spectral properties and below 310 ps duration are used for stroboscopic illumination at freely adjustable repetition rates. The performance of the source is demonstrated by characterizing the surface vibration field of a square-plate silicon MEMS resonator at 3.37 MHz. A minimum detectable vibration amplitude of less than 100 pm is reached.

Characterization of surface acoustic waves by stroboscopic white-light interferometry.

We present phase-sensitive absolute amplitude measurements of surface acoustic wave fields obtained using a stroboscopic white-light interferometer. The data analysis makes use of the high resolution available in the measured interferometric phase data, enabling the characterization of the out-of-plane surface vibration fields in electrically excited microstructures with better than 100 pm amplitude resolution. The setup uses a supercontinuum light source with tailored spectral properties for obtaining the high amplitude resolution. The duration of the light pulses is less than 300 ps to allow the detection of high frequencies. These capabilities enabled a detailed measurement of the focusing of surface acoustic waves by an annular interdigital transducer structure operating at 74 MHz, featuring a maximum vibration amplitude of 3 nm.

Simple visible supercontinuum light source with true continuous-wave output power

We present the concept and both the experimental and computational study of a simple supercontinuum light source emitting at temporally highly stable output powers. The principle of the light source is based on a standard pulsed supercontinuum source combined with fiber-based dispersive time-stretching. This approach allows for tailored spectral emission in the visible at a power stability of below 1%. Furthermore, the computation indicates that highly stable light emission with this concept does not necessarily require highest possible input pulse repetition rates and longest dispersive fiber lengths.

Full-field characterization of surface vibrations in microacoustic components by supercontinuum laser stroboscopic white-light interferometry

We present phase-sensitive absolute amplitude measurements of surface vibrations in microacoustic devices using a supercontinuum based stroboscopic white-light interferometer. The setup enables full-field characterization of out-of-plane vibration fields down to sub-100 pm amplitudes and up to GHz range, the highest detectable frequency limited only by the duration of the 300 ps light pulses. The capabilities of the system are demonstrated by measuring a vibration field in a square-plate silicon MEMS resonator at a 3.4 MHz resonance. The maximum vibration amplitude was measured to be 40 nm, and a minimum detectable amplitude limit of less than 100 pm was obtained.

Extremely white supercontinuum generation in three-hole suspended-core fiber

Microstructured optical fibers (MOFs) allow efficient generation of broadband supercontinuum spectra from narrow-band light sources. The spectral properties of supercontinua are thereby closely dependent on the tunable dispersion and nonlinear characteristics of the MOFs and can thus be tailored according to the requirements. Very high air filling factors of the cladding and extreme light confinement are reached by suspended-core MOFs, typically studied for sensing applications in the past [1–3].