Iosif Zeylikovich

Nonmechanical grating-generated scanning coherence microscopy

A novel method of coherence microscopy with a grating-generated delay line is demonstrated to produce depth-lateral images without axial or lateral scanning. A new image-reconstruction approach based on random phase modulation of the reference beam is realized. The depth-lateral reflections of test objects are digitally reconstructed with a simple algorithm.

Ultrashort Laguerre-Gaussian pulses with angular and group velocity dispersion compensation

Coherent optical vortices are generated from ultrashort 6.4 fs pulses. Our results demonstrate angular dispersion compensation of ultrashort 6.4 fs Laguerre-Gaussian (LG) pulses as well as what is believed to be the first direct autocorrelation measurement of 80 fs LG amplified pulses. A reflective-mirror-based 4f-compressor is proposed to compensate the angular and group velocity dispersion of the ultrashort LG pulses.

Spectral, temporal, and coherence properties of supercontinuum generation in microstructure fiber

Spectral, temporal, and coherence properties of supercontinuum (SC) generation in a microstructure fiber were experimentally studied with low-peak-power femtosecond pump pulses. By a spectral interferometry approach, the degree of mutual (axial) spectral coherence was observed to be low for solitons with a pump wavelength region close to the zero-dispersion wavelength (ZDW) and was observed to be high for the solitons with a pump wavelength region far from the ZDW. The generation of multiple frequency channels was experimentally demonstrated by dual time-delayed low-peak-power pump pulses near and far from the ZDW for possible application in a wavelength-division-multiplexing network.

Short coherence length produced by a spatial incoherent source applied for the Linnik-type interferometer

An axial resolution created by a spatial incoherent source is investigated theoretically and experimentally for the Linnik-type interferometer. The axial resolution in interference microscopy depends on both the temporal coherence length of the source and the objective numerical aperture (NA). Here the problem is treated in a more general situation by considering the spatial and temporal coherence of the illumination source which may be important for deep coherence imaging application. The results show that the axial resolution is degraded at the depth much less by using the optimal spectral bandwidth of the incoherent source and high-NA objectives.

Ultrafast dark-field interferometric microscopic reflectometry

A new method of ultrafast dark-field correlation interferometry from reflective microscopic objects is described. A 120-fs single-shot registration is achieved with a dynamic range of >35 dB, a sensitivity of <-50 dB, and a resolution of 15 mm. To demonstrate the potential of the method, we measured the thickness of single-mode fiber cladding to be 19 microm.

Observation of light diffraction by time-resolved femtosecond correlation interferometry.

We demonstrate time development of the diffraction of light waves from objects for what is to our knowledge the f irst time by using a new femtosecond correlation interferometry. This new dynamical optics method allows for the conversion of temporal information to space information with femtosecond resolution and has the potential to produce a time-resolved femtosecond movie for the visualization of light-wave propagation in space for scientific, biological, and medical applications.

HETERODYNE GRATING-GENERATED SCAN CORRELATION INTERFEROMETRY FOR REFLECTOMETRY AND SIGNAL-PROCESSING APPLICATIONS

A novel grating-generated scan correlation interferometry approach using a heterodyne technique for real-time signal processing is demonstrated. The characterization of reflections from a sample and detection of a femtosecond four-pulse train are presented as applications of the method.

Energy splitting of CdSe quantum dots induced by intense femtosecond laser excitation

Microscopic photoluminescence (PL) spectra of self-assembled CdSe quantum dots (QDs) grown by molecular beam epitaxy were investigated under excitation of intense femtosecond laser. Two samples with different QD sizes were fabricated. One had a single layer of larger CdSe QDs while the other had three layers of smaller QDs. The second harmonic radiation at 420 nm obtained from a mode-locked tunable Ti-Sapphire laser was used as the excitation source. The laser power density was in the order of kW cm−2 and the peak power density was in the order of GW cm−2 for the 150 fs laser pulse with a repetition rate of 78 MHz. The intense femtosecond laser pulses generated strong surface acoustic waves and modulated energy bands of electrons and holes of CdSe QDs. Increasing of the laser power resulted in the PL peak of the CdSe QDs splitting into four peaks for both QD samples: two peaks shifted to a lower energy side and the other two shifted to a higher energy side. The strong strain fields led to the mixing of he...

High resolution ultraviolet-to-visible image conversion using self-assembled CdSe/ZnCdMgSe quantum dot photoluminescence

High resolution ultraviolet-to-visible image conversion using photo-luminescence emitted by self-assembled CdSe/ZnCdMgSe quantum dots was investigated. The visible images centred at 585 nm with a resolution of 2 µm and 5 µm were obtained using a cw-He-Cd laser at the 325 nm excitation wavelength and with 150 fs laser pulses tuned to the second harmonic generation at 400 nm, respectively. The resolution limitations of visible images are discussed, and a high resolution optical system for the ultraviolet-to-visible image conversion is proposed.

High speed grating-generated electronic coherence microscopy of biological tissue without moving parts

A novel method of high speed grating-generated electronic coherence microscopy is applied to produce depth-lateral images of biological tissue without axial-lateral scanning. Axial-lateral scan is automatically performed by the stationary reflection diffraction grating installed in the Littrow configuration at the reference beam and a cylindrical lens installed in the sample beam. Using several 2D CCD array complex digital imags containing amplitude and phase values the depth-lateral reflections of biological tissue are reconstructed with a simple algorithm. The depth scan of 1.5 mm and the transversal coordinate image about 1.2 mm of the chicken tissue with a depth resolution of 17 micrometers , and a dynamic range about 70 dB are achieved. Final depth-lateral images are similar to OCT images and produced without any moving parts.