Distributed Feedback Dye Laser Research Articles

Highly Accurate Pneumatically Tunable Optofluidic Distributed Feedback Dye Lasers.

Optofluidic dye lasers integrated into microfluidic chips are promising miniature coherent light sources for biosensing. However, achieving the accurate and efficient tuning of lasers remains challenging. This study introduces a novel pneumatically tunable optofluidic distributed feedback (DFB) dye laser in a multilayer microfluidic chip. The dye laser device integrates microfluidic channels, grating structures, and vacuum chambers. A second-order DFB grating configuration is utilized to ensure single-mode lasing. The application of vacuum pressure to the chambers stretches the soft grating layer, enabling the sensitive tuning of the lasing wavelength at a high resolution of 0.25 nm within a 7.84 nm range. The precise control of pressure and laser tuning is achieved through an electronic regulator. Additionally, the integrated microfluidic channels and optimized waveguide structure facilitate efficient dye excitation, resulting in a low pump threshold of 164 nJ/pulse. This pneumatically tunable optofluidic DFB laser, with its high-resolution wavelength tuning range, offers new possibilities for the development of integrated portable devices for biosensing and spectroscopy.

All-in-One Optofluidic Chip for Molecular Biosensing Assays.

Integrated biosensor platforms have become subjects of high interest for consolidated assay preparation and analysis to reduce sample-to-answer response times. By compactly combining as many biosensor processes and functions as possible into a single lab-on-chip device, all-in-one point-of-care devices can aid in the accessibility and speed of deployment due to their compact size and portability. Biomarker assay preparation and sensing are functionalities that are often carried out on separate devices, thus increasing opportunity of contamination, loss of sample volume, and other forms of error. Here, we demonstrate a complete lab-on-chip system combining sample preparation, on-chip optofluidic dye laser, and optical detection. We first show the integration of an on-chip distributed feedback dye laser for alignment-free optical excitation of particles moving through a fluidic channel. This capability is demonstrated by using Rhodamine 6G as the gain medium to excite single fluorescent microspheres at 575 nm. Next, we present an optofluidic PDMS platform combining a microvalve network (automaton) for sample preparation of nanoliter volumes, on-chip distributed feedback dye laser for target excitation, and optical detection. We conduct concurrent capture and fluorescence tagging of Zika virus nucleic acid on magnetic beads in 30 min. Target-carrying beads are then optically excited using the on-chip laser as they flow through an analysis channel, followed by highly specific fluorescence detection. This demonstration of a complete all-in-one biosensor is a tangible step in the development of a rapid, point-of-care device that can assist in limiting the severity of future outbreaks.

Bragg order effect on ultrashort pulse generation by distributed feedback dye lasers under subnanosecond excitation: Numerical study

A comparative numerical study of the 1st- and 2nd-order distributed feedback (DFB) dye lasers pumped with 0.5 ns, 532 nm laser pulses is performed. A dynamic model of the gain-coupled DFB dye laser based on a coupled-wave theory and taking into account Bragg diffraction order is used. Due to the periodical distribution of the pump field and stimulated emission intensities along the excited dye volume, the rate equations of the population densities are turned into the equations of the Fourier coefficients. To simulate the DFB lasing, coupled-wave equations of optical fields are used. Effect of the pumping intensity on the temporal and energy characteristics of DFB dye lasers is studied depending on the dye concentration and the length of the excited dye volume. Influence of the lasing seed type (constant or noise-like) on the simulation results is also analyzed. A special emphasis is on the characteristics of single ultrashort (US) picosecond pulses generated by the relaxation oscillations mechanism. The results obtained indicate that for both types of DFB dye lasers the temporal course of the output intensity is governed by the pumping strength. Depending on the excess above the threshold (high or low), either US pulse trains or single US pulses are generated. The influence of the active medium parameters on their characteristics has been studied in detail. In addition, it was established that unlike the 1st-order DFB lasing, where the simulation results are independent of the seed type and smooth US pulses are always obtained, for the 2nd-order regime, to get smooth rather than structural single US pulses, a noise-like seed should be used. However, the most important finding is that the changeover from the 1st to the 2nd order leads to ∼1.1–3.2 (∼1.13–1.46) times reduction in duration, ∼1.4–3.4 (∼1.4–3.0)-fold increase in energy and ∼2.8–9.7 (∼1.5–4.8)-fold growth in peak power of single US pulses for the case of constant (noise-like) lasing seed. Hence, the use of the 2nd-order regime represents a simple and convenient way to improve the energy characteristics of single US pulses of DFB dye lasers generated by the relaxation oscillations mechanism.

Pneumatically tunable optofluidic DFB dye laser using corrugated sidewalls.

Polydimethylsiloxane-based optofluidics provides a powerful platform for a complete analytical lab-on-chip. Here, we report on a novel on-chip laser source that can be integrated with sample preparation and analysis functions. A corrugated sidewall structure is integrated into a microfluidic channel to form a distributed feedback (DFB) laser using rhodamine 6G dissolved in an ethylene glycol and water solution. Lasing is demonstrated with a threshold pump power of 87.9 µW, corresponding to a pump intensity of 52.7mW/cm2. Laser threshold and output power are optimized with respect to rhodamine 6G concentration and core index and found to be in good agreement with a rate equation model. Additionally, the laser can be switched on and off mechanically using a pneumatic cell inducing positive pressure on the grating.

Picosecond Pulse Generation by Second-Order Distributed Feedback Dye Laser

A Configuration of a second-order distributed feedback dye laser pumped by a nanosecond Nd:YAG laser is setup. The tuning range is narrower than that in the case of the first-order DFDL but lower noise and more stable is obtained. Single picoseconds pulse tunable in range of 543 to 596 nm can be observed by using different laser dyes. The tuning range is extended to the shorter wavelengths, which is closed to pumping wavelength.

Solid state distributed feedback laser using eosin blue dye

Solid state polymeric samples were prepared by doping eosine blue dye with MMA. Laser light emitted from the solid polymeric sample was attained by second harmonic Nd:YAG laser. Polymeric film coated prism was used to produce distributed feedback dye laser (DFDL). The output energy of DFDL was measured at the emission peaks of different pump powers and dye concentrations. Tunability of wavelength over 30 nm was evidenced. Slope efficiency was also determined for different pump powers. Thermal stability of eosin blue dye doped with methyl methacrylate (MMA) was observed.

The dynamics of gain-coupled distributed feedback dye laser: feedback mechanism and laser field evolution

The temporal and spatial evolution of the two counter-propagating laser waves inside the active medium of a gain coupled distributed feedback dye laser is studied via a dynamic model. More specifically, the feedback mechanism, the temporal and spatial evolution of laser waves, the interaction between them, and the effect of pump pulse characteristics on the feedback strength are explained. It is shown that a pumping configuration with a spatial Gaussian pattern strongly decreases the laser pulse energy. This has never proposed or described by other models in the literature. For a narrow Gaussian pump pulse, the distributed feedback lasing on both sides of the active medium vanishes and causes further dissipation of stored energy in the form of spontaneous emission.

Improving the Performance of Gold-Nanoparticle-Doped Solid-State Dye Laser Using Thermal Conversion Effect

Energy transfer between spherical gold nanoparticles with size of more than 15 nm and molecules of organic dye 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM) has been studied. Such radiative energy transfer led to high local temperature, giving rise to a bleaching effect that resulted in rapid degradation of the laser medium. Gold nanoparticles were dispersed at concentrations from 5 × 109 particles/mL to 5 × 1010 particles/mL in DCM polymethylmethacrylate polymer using a radical polymerization process with 2,2′-azobis(isobutyronitrile) (AIBN) as initiator. Using the fast thermoelectric cooling method, the laser medium stability was significantly improved. The output stability of a distributed feedback dye laser pumped by second-harmonic generation from a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser was investigated. Moreover, bidirectional energy transfer between gold nanoparticles and dye molecules was observed.

Development of UV Laser Source Based on Distributed Feedback Dye Lasers Foruse in Measurement of Ozone in the Lower Atmosphere

We conducted a study to develop a transmitter consisting of two Distributed Feedback Dye Lasers (DFDL) using Rhodamine 6G as an active medium, pumped by a frequency-doubled Nd:YAG laser (5ns, 10 Hz, 532 nm). The BBO crystals are used for frequency-doubling of DFDLs to generate UV missions. This system has been set up and it generates selected wavelenghts at 282.9 nm and 286.4 nm with the energy of 30 \(\mu\)J/pulse and 60 \(\mu\)J/pulse respectively. A DIAL system using this UV transmitter is designed to measure the vertical distribution of ozone with high temporal and spatial resolution. Our simulations of received DIAL signal indicate that the altitude of ozone distribution measurement can reach to over 5000 m along with range resolution of 100 m.

Energy transfer studies for the liquid and solid state materials of Rhodamine B and Styryl 7 Dye

Samples of dye doped Rhodamine B and Styryl 7 with MMA in solid state and the dye mixture in liquid state were prepared. Frequencydoubled Nd-YAG laser was used to evaluate solid and liquid dye samples laser emission. Using dye cell and dye-coated prism setup, distributed feedback dye laser(DFDL) activity was initiated. The dependence of pulse widths, and output power on acceptor – donor concentrations and pump power were analyzed in theoretical form. The resulting output energy of DFDL for liquid and solid sampling were checked at high emission levels of donor and acceptor dyes for various pump powers and acceptor-donor concentrations and were compared with theroretical results. To identify the thermal stability of solid pattern, the differential thermal analysis(DTA) and Thermogravimetric analysis(TGA) were performed. By adjusting the prism arrangement, for liquid and solid samples continuous tunability was observed from 570 to 727nm.

Spectral evolution of distributed feedback laser of gold nanoparticles doped solid-state dye laser medium

Characteristics of suppressed relaxation oscillation of a distributed feedback dye laser (DFDL) based on the energy transfer process in a mixture of spherical gold nanoparticles-doped solid-state polymethylmetacrylate dissolved 4-(Dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran dye was theoretically and experimentally studied. Single pulse generation regime of the DFDL can be obtained with a suitable gold nanoparticle concentration and ratio of pump power over lasing threshold. Numerical analysis and experimental approach showed that in this regime, the first-pulse laser pulsewidth is rather unchanged while varying the gold nanoparticles concentration in the range of 2.0 × 109–2.0 × 1010 par cm−3. The enhancement of first pulse and the suppression of the secondary pulses by bi-direction energy transfer of spherical gold nanoparticles were experimentally observed.

Temporal output profile of gain-coupled distributed feedback dye laser

The lasing mechanism and temporal output profile of distributed feedback dye lasers is investigated, using a model based on induced polarization in the dye solution, where a more accurate behavior of the laser output is predicted. It is found that the temporal output profile of the laser is mostly determined by the concentration of dye solution and the lifetime of the upper laser level of dye molecules. To a large extent, the results of this work agree with experimental studies, even at high-level pump intensities where the self Q-switched model fails to be applied. Especially, the experimentally observed irregular intensity profile of laser output is explained. It is also shown that, when pumping dye solution by narrower pulses, the single-pulse output mode can be realized in the wider range of pump intensities and the pulsewidth stability of laser can be improved.

Tunable organic distributed feedback dye laser device excited through Förster mechanism

Tunable organic distributed feedback (DFB) dye laser performances are re-investigated and characterized. The slab-type waveguide DFB device consists of air/active layer/glass substrate. Active layer consisted of tris(8-quinolinolato)aluminum (Alq3), 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM) dye, and polystyrene (PS) matrix. Effective energy transfer from Alq3 to DCM through Forster mechanism enhances the laser emission. Slope efficiency in the range of 4.9 and 10% is observed at pump energy region higher than 0.10–0.15 mJ cm−2 (lower threshold), which is due to the amplified spontaneous emission (ASE) and lasing. Typical slope efficiency for lasing in the range of 2.0 and 3.0% is observed at pump energy region higher than 0.25–0.30 mJ cm−2 (higher threshold). The tuning wavelength for the laser emission is ranged from 620 to 645 nm depending on the ASE region.

The effect of pulsewidth of pumping pulse on the stability of distributed feedback dye laser

The generation of a single and stable picosecond pulse by distributed feedback dye laser is investigated in this work. The numerical result for the rate equation system that includes the thermal effects in the lasing medium is provided. By applying this model to Rhodamine 6G, it is found that considerable improvement in the stability of the laser can be achieved by pumping the system with narrower laser pulses. The simulation shows that if the dye solution is pumped by sub-200 ps pulse, the laser can be operated in single-pulse output mode with acceptable stability in pulsewidth over a long range of pumping intensity. This result is confirmed by a more complicated model composed of non-averaged Maxwell and rate equations. Even though the thermal effects do not play a significant role in equivalent cavity lifetime, they result in considerable wavelength shift toward the shorter wavelengths.

Multiline distributed feedback dye laser endorses Wien’s displacement law

Peak spectral intensity shifting in a distributed feedback dye laser (DFDL) supporting multiple lines in 550 to 570 nm range is reported. A 3 mM solution of Rh6G in ethanol is pumped with a complex interference pattern of multiple Q-switched and mode-locked frequency-doubled Nd:YAG laser pulses for obtaining numerous discrete laser lines to study the impact of temperature buildup on resonant frequency shifting characteristics. Multiple pulses pumped DFDL are operated at five and nine wavelengths in two separate arrangements and spectra recorded without changing exciting pulses intensities and angles. Higher intensity lines are found to shift during operation from longer to shorter wavelengths due to gradual temperature rise in the dye solution. Laser lines associated with relatively higher intensities shift from lower to higher frequency parts of emission spectrum due to accumulative temperature rise. This temperature-dependent peak intensity drift occurrence becomes faster by reducing the pumping laser interpulse periods. This paper reports gradual heat accumulation stipulated spectral intensity shifts of laser lines in multiline DFDL, which appears to be compliant with Wien’s displacement law.

Polymer distributed feedback dye laser with an external volume Bragg grating inscribed in a nanocomposite by holographic technique

We report on a thin-film polymer distributed feedback (DFB) laser, composed of an active waveguide and an external volume Bragg grating providing second-order distributed feedback, and its output properties. The volume noncorrugated Bragg gratings were inscribed holographically in an organic–inorganic nanocomposite containing high refractive index inorganic nanoparticles. The active waveguide doped with PM576 was fabricated on top of the Bragg grating. The DFB laser presented exhibits both surface and edge emission by transverse optical pumping with nanosecond laser pulses at 532 nm. A theoretical model to analyze the influence of the parameters of the active waveguide and the Bragg grating on the laser performance has been developed.

Influence of ZnO nanoparticles on Coumarin-503 and Coumarin-540 dye mixture for energy transfer distributed feedback dye lasers

Using organic dyes Coumarin-503 (C503) and Coumarin-540 (C540) as donor and acceptor dyes, respectively, and Nd-YAG as pumping source (355 nm), an energy transfer-distributed feedback dye laser (ETDFDL) was constructed and its characteristics studied. Theoretical studies such as critical transfer radius (Ro), critical concentration (Co), and half quenching concentration (C1/2) were carried out using the absorption and fluorescence spectra of donor and acceptor dyes. On varying the input pump energy to the nanoparticle-incorporated ETDFDL and keeping the acceptor and donor dye concentrations constant, the lasing output obtained was found to be higher than that without the use of nanoparticles. This enhancement was due to the size, shape, and coupling between nanoparticles with the dye mixture. Tunability in the range of 435–553 nm was obtained for both donor (C503) and acceptor (C540) DFDL as a function of the angle of interfering beams of the pump laser.

Highly efficient solid-state distributed feedback dye laser based on polymer-filled nanoporous glass composite excited by a diode-pumped solid-state Nd:LSB microlaser.

Realization of a compact, robust, highly stable, and efficient solid-state distributed feedback (DFB) dye laser based on pyrromethene 580-doped modified poly-(methyl methacrylate) embedded into nanoporous glass host is reported. A diode-pumped solid-state STA01SH-500 Nd:LSB microlaser (λ=532 nm; τ0.5∼0.5 ns; EP≤80 μJ; f≤500 Hz) is used as a pump source. When pumped well above threshold, a DFB laser emits a train of ultrashort pulses (τ≤1 ns; τ0.5<0.5 ns; Δλ0.5≤0.01 nm), while at excitation intensities not far from threshold, single transform-limited picosecond pulses (τ0.5≤40 ps; τ0.5Δν0.5∼0.3), tunable from 541 to 598nm, are generated. The DFB lasing efficiency reaches ∼60% upon an energy stability of ∼1.4% and an overall service life of the active element of ∼9×107 laser shots. More than an order of magnitude increase in the temperature stability of a lasing wavelength as compared with ethanol solutions of laser dyes is practically demonstrated.

High frame rate multi-resonance imaging refractometry with distributed feedback dye laser sensor

High frame rate and highly sensitive imaging of refractive index changes on a surface is very promising for studying the dynamics of dissolution, mixing and biological processes without the need for labeling. Here, a highly sensitive distributed feedback (DFB) dye laser sensor for high frame rate imaging refractometry without moving parts is presented. DFB dye lasers are low-cost and highly sensitive refractive index sensors. The unique multi-wavelength DFB laser structure presented here comprises several areas with different grating periods. Imaging in two dimensions of space is enabled by analyzing laser light from all areas in parallel with an imaging spectrometer. With this multi-resonance imaging refractometry method, the spatial position in one direction is identified from the horizontal, i.e., spectral position of the multiple laser lines which is obtained from the spectrometer charged coupled device (CCD) array. The orthogonal spatial position is obtained from the vertical spatial position on the spectrometer CCD array as in established spatially resolved spectroscopy. Here, the imaging technique is demonstrated by monitoring the motion of small sucrose molecules upon dissolution of solid sucrose in water. The omission of moving parts improves the robustness of the imaging system and allows a very high frame rate of up to 12 Hz.

Refractometric monitoring of dissolution and fluid flow with distributed feedback dye laser sensor.

Monitoring the dissolution of solid material in liquids and monitoring of fluid flow is of significant interest for applications in chemistry, food production, medicine, and especially in the fields of microfluidics and lab on a chip. Here, real-time refractometric monitoring of dissolution and fast fluid flow with DFB dye laser sensors with an optical imaging spectroscopy setup is presented. The dye laser sensors provide both low detection limits and high spatial resolution. It is demonstrated how the materials NaCl, sucrose, and bovine serum albumin show characteristic dissolution patterns. The unique feature of the presented method is a high frame rate of up to 20 Hz, which is proven to enable the monitoring of fast flow of a sucrose solution jet into pure water.