Yu. M. Zadiranov

High-power picosecond and femtosecond pulse generation from a two-section mode-locked quantum-dot laser

We demonstrate mode locking in a two-section quantum-dot laser that produces output powers up to 45 mW at 1260 nm. The pulse duration could be varied from 2 ps to as short as 400 fs at the 21 GHz pulse repetition rate.

Ordered porous diamond films fabricated by colloidal crystal templating

We have developed a colloidal crystal templating method for preparation of diamond films with 2D and 3D ordered porous structures. The technological process involved breaks down into (a) impregnation into the pores of silica colloidal crystal (opal) films of detonation nanodiamond (DND) particles from their hydrosol; (b) microwave plasma-enhanced chemical vapor deposition (MWPECVD) regrowth with diamond of pores with high DND filling; (c) Ar(+) ion dry etching of fragments of shells of coalesced diamond crystallites which form in the course of MWPECVD on the surface of the SiO(2) beads making up the outer surface of a film and (d) wet etching of the SiO(2) template in aqueous HF solution. The final samples are either connected to the substrate or free-standing films of various thicknesses having 2D or 3D ordered porous structures. The morphology of the diamond films fabricated by this method replicates the pore network of the opal template. Raman measurements confirm the diamond structure of the synthesized ordered porous material.

Experimental Demonstration of Reduced Light Absorption by Intracavity Metallic Layers in Tamm Plasmon-based Microcavity

We demonstrate experimentally a microcavity based on SiO2/TiO2 with two gold layers directly attached to the central base of the microcavity. The design of optical modes based on the peculiarities of Tamm plasmons provides reduced absorption due to the fixing of the node of the electric field of optical mode to metallic layers. Experimentally measured reflection and transmission spectra exhibits three features, corresponding to three hybrid modes of the microcavity. The widths of spectral features confirm that absorption of light by metallic layers is vanishing for optimized mode. The latter is confirmed by resonant transmission of light through the structure. In case of the laser structure, two intracavity metallic layers could serve as contacts for electrical pumping.

Single-spatial-mode semiconductor VCSELs with a nonplanar upper dielectric DBR

Single-spatial-mode semiconductor vertical-cavity surface-emitting lasers (VCSELs) with a non-planar upper (output) dielectric distributed Bragg reflector (DBR) for the 850 nm spectral region are fabricated. The suggested design provides stable single-mode generation in the entire range of working currents, limited by overheating of the active region. Devices with intracavity contacts and a comparatively large current-aperture diameter (5–6 μm) exhibit single-mode lasing at a wavelength of 840–845 nm in the continuous-wave mode at room temperature with threshold currents of 1.2–1.3 mA, a differential efficiency of 0.5–0.55 mW mA−1, and anoutput power of up to 2 mW.

High-temperature lasing in a microring laser with an active region based on InAs/InGaAs quantum dots

Lasing at a wavelength of >1.3 μm has been achieved at temperatures of up to 380 K in a ring microlaser (diameter of 6 μm) with an active region based on InAs/InGaAs quantum dots.

A decrease in ohmic losses and an increase in power in GaSb photovoltaic converters

The transmission-line model with radial and rectangular geometry of contact pads has been used to study the contact systems Cr-Au, Cr-Au-Ag-Au, Ti-Pt-Au, Pt-Ti-Pt-Au, Pt-Au, Ti-Au, Ti-Pt-Ag, Ti-Pt-Ag-Au, and Pt-Ag deposited on the p-GaSb surface by the methods of magnetron sputtering and resistive evaporation. It is established that the contact systems Ti-Pt-Ag-Au and Ti-Pt-Ag exhibit the smallest values of the specific contact resistance (ρc ≤ 10−6 Ω cm2), which makes it possible to use these systems in fabrication of photovoltaic converters generating photocurrents with densities as high as 15 A/cm2.

Mode selection in InAs quantum dot microdisk lasers using focused ion beam technique

Optically pumped InAs quantum dot microdisk lasers with grooves etched on their surface by a focused ion beam are studied. It is shown that the radial grooves, depending on their length, suppress the lasing of specific radial modes of the microdisk. Total suppression of all radial modes, except for the fundamental radial one, is also demonstrated. The comparison of laser spectra measured at 78 K before and after ion beam etching for a microdisk of 8 μm in diameter shows a sixfold increase of mode spacing, from 2.5 to 15.5 nm, without a significant decrease of the dominant mode quality factor. Numerical simulations are in good agreement with experimental results.

Absorption in laser structures with coupled and uncoupled quantum dots in an electric field at room temperature

The absorption of uncoupled and tunnel-coupled vertically correlated quantum dots (QDs), measured at room temperature, has been experimentally compared. It is revealed that matching of the laser wavelength and Stark shift for laser structures with tunnel-coupled QDs leads to resonant absorption with formation of bound and antibound exciton states with a splitting energy of ∼62 meV between them in QD molecules. For these states, an external field causes a large linear Stark shift (up to 68 meV). For uncoupled QDs, one resonant absorption peak with the formation of an exciton (for which the Stark shift does not exceed 13 meV) is observed.

On the gain properties of “thin” elastically strained InGaAs/InGaAlAs quantum wells emitting in the near-infrared spectral region near 1550 nm

The results of experimental studies of the gain properties of “thin” (3.2 nm thick) elastically strained InGaAs/InGaAlAs quantum wells emitting in the near-infrared spectral region near 1550 nm are presented. The results of studying the threshold and gain characteristics of stripe laser diodes with active regions based on “thin” quantum wells with a lattice–substrate mismatch of +1.0% show that the quantum wells under study exhibit a high modal gain of 11 cm–1 and a low transparency current density of 46 A/cm2 per quantum well.

Free-standing optical filters for a nanolithography source operating in the 12–15 nm wavelength range

Optical filters in the form of free-standing multilayer films have been obtained for a nanolithography source operating in the 12–15 nm range of wavelengths. A method for the synthesis of such filters is described.