Yu. P. Voinov

Optical properties of a carbon-zirconia quantum-dot photonic crystal

We report the optical properties of a new type of photonic crystal: a transparent fused silica matrix containing quantum dots—nanoparticles of another material. In this study, nanoparticles consist of graphite zones several nanometers in size, stabilized by zirconia. The photonic crystal is prepared by high-temperature annealing (1200°C) of synthetic opal infiltrated with zirconia and a small amount of carbon. We demonstrate selective reflection of visible light from the surface of the quantum-dot crystal under broadband illumination. Such crystals are potentially attractive as narrow-band selective filters that would reflect the exciting light in Raman measurements and might be used to convert short-wavelength broadband radiation to quasi-monochromatic light in the visible range.

Reduction of the threshold of stimulated Raman scattering in Raman-active media introduced into pores of a globular photonic crystal

The characteristics of stimulated Raman scattering in benzene and carbon disulfide introduced in pores of globular photonic crystals—opal matrices formed from close-packed balls (globules) of amorphous quartz (silica)—have been experimentally studied. Stimulated Raman scattering spectra have been excited by giant pulses of the second optical harmonic (532 nm) of a YAG laser. The spectra have been recorded in the direction of mirror reflection from the (111) growth surface of a globular photonic crystal at various angles of incidence (10°–70°) of laser radiation. It has been shown that the threshold of stimulated Raman scattering decreases sharply (by more than an order of magnitude) at a certain angle of mirror reflection and additional Stokes and anti-Stokes Raman satellites appear in the spectrum. The observed sharp decrease in the threshold of stimulated Raman scattering has been explained by an increase in the spectral density of the electromagnetic field in the surface region of the photonic crystal because of the approach of the spectral position of the stopband of the photonic crystal to the exciting line (532 nm) under variation of the angle of incidence of pump radiation on the (111) surface.

Reflectivity spectra of gold- and silver-infiltrated opals

We have studied the optical properties of gold- and silver-infiltrated opal photonic crystals composed of close-packed SiO2 spheres ∼200 nm in diameter. The reflectivity spectra obtained are used to assess the photonic band gap of the crystals in the visible range. We present the characteristics of the emission induced in the opal photonic crystals by monochromatic and broadband light sources and calculated reflectances of the synthetic opal samples.

Resonance excitation of photoluminescence in sodium uranyl acetate crystals

The photoluminescence spectra of sodium uranyl acetate polycrystals are recorded under excitation by different sources (semiconductor light-emitting diodes, cw lasers, and repetitively pulsed lasers). The excitation wavelengths fall into the absorption band of this solid, which makes it possible to record photoluminescence beginning from an extremely small volume of the material (10–10 cm3) at exposures of ~10–3 s.

Second optical harmonic near the surface of ferroelectric photonic crystals and photon traps

This paper reports on the results of experimental investigations of the generation of the second optical harmonic localized in a thin subsurface layer of ferroelectric photonic crystals and photon traps. To excite the second optical harmonic, a KGW: Yb solid-state pulsed-periodic laser generating the radiation with a wavelength of 1026 nm in a form of pulses ∼10−13 s long with a repetition frequency of 200 kHz at the average power of 0.1–3.5 W and power density of ∼109−1012 W/cm2 in a spot less than 100 μm in diameter focused near the surface was used. Ferroelectrics, notably, barium titanate or sodium nitrite, were introduced into the pores between SiO2 nanoglobules. It is established that the maximal conversion efficiency of the exciting radiation into the second optical harmonic was several percents. The generation characteristics of the second optical harmonic near the surface of photonic crystals filled with ferroelectrics are compared with the generation of the second optical harmonic in ferroelectric photon traps of barium titanate ceramics and sodium nitrite microcrystals.

Local spectroscopy of band gaps in ferroelectric photonic crystals

We have measured visible to near-UV reflection spectra of opal photonic crystals infiltrated with ferroelectrics: barium titanate, sodium nitrite, potassium iodate, and triglycine sulfate. An experimental procedure has been developed for the infiltration of various ferroelectrics into opal pores through laser ablation and laser implantation. Using a fiber-optic probe, we were able to analyze surface reflection spectra of photonic crystals with a 0.2-mm resolution. A deuterium lamp was used as a broadband UV source, which allowed us to observe both the first and second [111] photonic band gaps in the reflection spectrum of opal crystals.

The Reflectance Spectra of Photonic Crystals with Embedded Ferrite Inclusions

Results of optical properties investigations of photonic crystals, filled by ferrites, are presented. The photonic crystals consist of amorphous SiO2 spherical nanoclusters. Pores of the crystals were filled by ferrites , where . Reflectance spectra were studied in visible range. It was shown that the reflectivity of the fabricated magnetophotonic crystals increases up to 80% under magnetization.

Optical properties of three-dimensional magnetic opal photonic crystals

We have studied the optical properties of opal photonic crystals infiltrated with the M0.35Zn0.65Fe2O4 (M = Ni, Co) ferrites. The crystals consisted of amorphous SiO2 nanospheres. The visible reflectivity spectra of the crystals were used to determine parameters of their photonic band gap and their refractive index.

Band-gap spectroscopy of mesoporous one-dimensional photonic-crystal alumina based films

Mesoporous photonic-crystal alumina based films are synthesized by the anodic etching of thin aluminum plates. The transmission and reflection spectra of the synthesized films in a wide spectral range including several primary band gaps are given. Some microscopic parameters of samples are calculated, and the transmission and reflection spectra are plotted for the first six band gaps alongside with photon dispersion curves.

Spectra of secondary emission during generation of optical harmonics in globular photonic crystals

Secondary emission spectra of globular silica photonic crystals when their surfaces were exposed to laser pulses 250 fs long at a power density to 1 TW/cm2 have been studied. Optical harmonics and plasma emission were detected in this case. For the opal matrix containing pores filled with air, in the reflection mode, the third optical harmonic with a conversion efficiency of ∼10% arises. The highest conversion efficiency for exciting radiation with wavelengths of 1026 or 513 nm is implemented when the frequencies of the exciting radiation or the second harmonic are near the stop band edge. In globular photonic crystals filled with sodium nitrite or barium titanate ferroelectrics, the second optical harmonic is observed. The exciting radiation conversion efficiency to the second optical harmonic was a few percent and depended on the frequency of exciting radiation and photonic crystal globule diameters. It is found that the plasma emission intensity increases with the exciting radiation power density. The dependences of the intensity of the second and third optical harmonics on the pump intensity are constructed for various photonic crystal globule diameters.