Feedback Laser Emission Research Articles

Light-Controlled Direction of Distributed Feedback Laser Emission by Photo-Mobile Polymer Films.

We report on the realization of Distributed Feedback (DFB) lasing by a high-resolution reflection grating integrated in a Photomobile Polymer (PMP) film. The grating is recorded in a recently developed holographic mixture basically containing halolakanes/acrylates and a fluorescent dye molecule (Rhodamine 6G). The PMP-mixture is placed around the grating spot and a subsequent curing/photo-polymerization process is promoted by UV-irradiation. Such a process brings to the simultaneous formation of the PMP-film and the covalent link of the PMP-film to the DFB-grating area (PMP-DFB system). The PMP-DFB allows lasing action when optically pumped with a nano-pulsed green laser source. Moreover, under a low-power light-irradiation the PMP-DFB bends inducing a spatial readdressing of the DFB-laser emission. This device is the first example of a light-controlled direction of a DFB laser emission. It could represent a novel disruptive optical technology in many fields of Science, making feasible the approach to free standing and light-controllable lasers.

Generalized extreme-value distribution of maximum intensities and Lévy-like behavior in an SOA-based random feedback laser emission

We report on generalized extreme value distribution of the maximum output intensities in a random feedback laser (RFL) emission, with localized gain provided by a semiconductor optical amplifier (SOA). Feedback due to Rayleigh backscattering from a single-mode fiber sustains the laser oscillation in a half-open cavity configuration. The experimental distribution of maximum output intensities near threshold is described by Fréchet distribution, and the distribution of intensities is associated with a heavy-tail power-law distribution. Increasing the pump above the threshold, the distribution of maxima tends to a Gumbel distribution. We also present experimental evidence of Lévy-like behavior in the SOA-RFL output intensities operating near the laser threshold, which is in agreement with extreme value statistics predictions.

Regenerated cellulose as a porous silica composite template for random laser emission

Scattering medium diffuses light, which normally is not interesting for photonic applications. However, multiple scattering allows trapping light inside of a material, increasing the photon lifetime that can be amplified by a gain medium. Therefore, such scatters distribution combined with light amplification is one of the main principles of random laser phenomena. Here, we described an innovative way to produce highly porous material; porous cellulose to deposit an aluminoxane–epoxy–siloxane hybrid, which can be used as a template for random laser application. The sol–gel methodology was employed to obtain the porous cellulose and Boehmite-GPTS hybrids. The composite (cellulose plus hybrid) was heated at 600 °C to decompose the cellulose fiber, generating a 3D porous alumina–silica network, to which a Rhodamine B ethanol solution was added to act as the laser gain medium. Samples were fully characterized, and random laser studies were performed by using the second harmonic (532 nm) of a Nd:YAG laser with pulse width of 100 ps as the excitation source. Incoherent feedback laser emission was detected for samples pumped with fluences higher than 62 mJ/mm2. Laser characteristics, such as fluence threshold and emission band width were determined.

Multicolored Emission and Lasing in DCM-Adamantane Plasma Nanocomposite Optical Films.

We present a low-temperature versatile protocol for the fabrication of plasma nanocomposite thin films to act as tunable emitters and optical gain media. The films are obtained by the remote plasma-assisted deposition of a 4-(dicyano-methylene)-2-methyl-6-(4-dimethylamino-styryl)-4H-pyran (DCM) laser dye alongside adamantane. The experimental parameters that determine the concentration of the dye in the films and their optical properties, including light absorption, the refractive index, and luminescence, are evaluated. Amplified spontaneous emission experiments in the DCM/adamantane nanocomposite waveguides show the improvement of the copolymerized nanocomposites' properties compared to films that were deposited with DCM as the sole precursor. Moreover, one-dimensional distributed feed-back laser emission is demonstrated and characterized in some of the nanocomposite films that are studied. These results open new paths for the optimization of the optical and lasing properties of plasma nanocomposite polymers, which can be straightforwardly integrated as active components in optoelectronic devices.

Near-infrared distributed feedback laser emission based on cascade Förster resonance energy transfer to Nile Blue aggregates

We present the real time tunable distributed feedback lasing in the region of near-infrared light obtained in a dye doped polymeric layer via cascade energy transfer based on Förster resonance (FRET). The Rhodamine 6G and Rhodamine B laser dyes were used as a donor for FRET effect, while the Nile Blue dye served as an acceptor. The shift of the emission from visible to near-infrared region was possible due to the formation of the dyes aggregates of lower than for molecules energy levels. Therefore, through the sequence of energy transfers between molecules and aggregates, the shift between excitation and stimulated emission spectra of about 200 nm can be achieved. The use of the periodically modulated pumping beam from pulsed Nd:YAG laser allows to select and amplify particular wavelength from the gain profile according to Bragg conditions, what can be easily tuned by changing the period of the interference pattern. The reported tunability of distributed feedback emission from 725 nm to 745 nm confirmed that only Nile Blue aggregates were involved in the laser action, while donor molecules and aggregates, as well as acceptor in non-aggregated form, acted as a canal for energy transfer.

First Highly Efficient and Photostable E and C Derivatives of 4,4‐Difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BODIPY) as Dye Lasers in the Liquid Phase, Thin Films, and Solid‐State Rods

A new library of E- and C-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) derivatives has been synthesized through a straightforward protocol from commercially available BODIPY complexes, and a systematic study of the photophysical properties and laser behavior related to the electronic properties of the B-substituent group (alkynyl, cyano, vinyl, aryl, and alkyl) has been carried out. The replacement of fluorine atoms by electron-withdrawing groups enhances the fluorescence response of the dye, whereas electron-donor groups diminish the fluorescence efficiency. As a consequence, these compounds exhibit enhanced laser action with respect to their parent dyes, both in liquid solution and in the solid phase, with lasing efficiencies under transversal pumping up to 73 % in liquid solution and 53 % in a solid matrix. The new dyes also showed enhanced photostability. In a solid matrix, the derivative of commercial dye PM597 that incorporated cyano groups at the boron center exhibited a very high lasing stability, with the laser emission remaining at the initial level after 100 000 pump pulses in the same position of the sample at a 10 Hz repetition rate. Distributed feedback laser emission was demonstrated with organic films that incorporated parent dye PM597 and its cyano derivative. The films were deposited onto quartz substrates engraved with appropriate periodical structures. The C derivative exhibited a laser threshold lower than that of the parent dye as well as lasing intensities up to three orders of magnitude higher.

Carboxylates versus Fluorines: Boosting the Emission Properties of Commercial BODIPYs in Liquid and Solid Media

AbstractA new and facile strategy for the development of photonic materials is presented that fufills the conditions of being efficient, stable, and tunable laser emitters over the visible region of spectrum, with the possibility of being easily processable and cost‐effective. This approach uses poly(methyl methacrylate) (PMMA) as a host for new dyes with improved efficiency and photostability synthesized. Using a simple protocol, fluorine atoms in the commercial (4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene) (F‐BODIPY) by carboxylate groups. The new O‐BODIPYs exhibit enhanced optical properties and laser behavior both in the liquid and solid phases compared to their commercial analogues. Lasing efficiencies up to 2.6 times higher than those recorded for the commercial dyes are registered with high photostabilities since the laser output remain at 80% of the initial value after 100 000 pump pulses in the same position of the sample at a repetition rate of 30 Hz; the corresponding commercial dye entirely loses its laser action after only 12 000 pump pulses. Distributed feedback laser emission is demonstrated with organic films incorporating new O‐BODIPYs deposited onto quartz substrates engraved with appropriated periodical structures. These dyes exhibit laser thresholds up to two times lower than those of the corresponding parent dyes with lasing intensities up to one order of magnitude higher.

Multimode distributed feedback laser emission in a dye-doped optically pumped polymer thin film

Multimode distributed feedback laser emission in a dye-doped optically pumped polymer thin film

Multimode distributed feedback laser emission in a dye-doped optically pumped polymer thin-film

We report on particular features of thin film distributed feedback (DFB) lasers. Devices are optically pumped using a Lloyd-mirror interferometer. For a given DFB grating period, the number of lasing modes is film thickness dependent. Spectral content of the devices is analysed using planar waveguide theory. An excellent agreement between the theoretical transverse electric mode structure and the laser emission spectrum is found.

Two-photon-pumped distributed feedback zirconia waveguide lasers

Distributed feedback laser action of narrow line-width output was demonstrated in zirconia waveguides doped with trans-4-[p-(N-hydroxyethyl-N-methylamino) styryl]-N-methylpyridinium p-toluene sulfonate, a compound of strong two-photon up-converted emission near 620 nm. Single-beam pumping at 1.06 μm led to intense up-converted amplified spontaneous emission at 620 nm. Transient gratings for coherent scattering were generated in the waveguides by crossing two 1.06-μm beams. Narrow line-width distributed feedback laser emission was observed at 627 nm.

Oligo(phenylethynylene) as a High Photoluminescence Quantum Yield Material and Its Distributed Feedback Laser Emission in Thin Films

The high photoluminescence quantum yield of phenylethynylene oligomers (see Figure for chemical formula) capped by different terminal groups, such as naphthyl or benzyl benzoates, coupled with their good solubility has led to their introduction as chromophores in a polymer matrix of poly(vinylcarbazole) for laser emission studies.

Realization and characterization of optically pumped GaInN-GaN DFB lasers

Room-temperature (RT) operation of optically pumped GaN-GaInN distributed-feedback (DFB) lasers is demonstrated in the spectral range from 400 to 415 nm. The ridge-waveguide distributed feedback lasers were realized by dry etching on a GaN-GaInN double heterostructure. Laser emission was observed in the entire spectral range of optical gain, which was determined by amplified spontaneous emission (ASE) measurements. The wavelength shift of the distributed feedback laser emission with temperature was investigated. An array of DFB lasers with different grating periods allowed to obtain the spectral dependence of the laser threshold and the effective refractive index of the GaN-GaInN lasers. The lowest laser threshold we achieved was 0.95 MW/cm/sup 2/.