Organic Solid-state Lasers Research Articles

Low-Loss Optical Waveguide and Highly Polarized Emission in a Uniaxially Oriented Molecular Crystal Based on 9,10-Distyrylanthracene Derivatives

A uniaxially oriented crystal based on 9,10-bis(2,2-di-p-tolylvinyl)anthracene (BDTVA) with an excellent waveguide and polarization performance has been prepared. The low loss coefficient (2.75 cm–1) and the high polarization contrast (0.72) may result from the uniaxially oriented packing and layer-by-layer molecular structure in the BDTVA crystal. Moreover, amplified spontaneous emission is observed from the BDTVA crystal with a low threshold of 265 μJ/cm2, and the gain coefficient is 52 cm–1 at the peak wavelength of 509 nm. These features indicate that the BDTVA crystal may be potentially applied in the field of optical waveguides and organic solid-state lasers.

Red emissive diarylboron diketonate crystals: aggregation-induced color change and amplified spontaneous emission

The present study not only provides a rare example of organic crystals with highly efficient red fluorescence but also indicates the possible application of four-coordinate boron materials in organic solid-state lasers.

The molecular picture of amplified spontaneous emission of star-shaped functionalized-truxene derivatives

Organic optical gain materials are the basis for organic solid-state lasers.

Thermal effects in thin-film organic solid-state lasers.

With the recent development of organic solid-state lasers (OSSLs) architectures enabling power scaling and progresses towards continuous-wave operation, the question of thermal effects now arises in OSSLs. In this paper, a Rhodamine 640-PMMA based vertical external cavity surface emitting organic laser is investigated. A thermal microscope is used to record temperature maps at the organic thin film surface during laser action; those maps are compared with time-resolved finite element thermal simulations. The measured and simulated peak temperature rises are in good accordance and are shown to remain below 10 K in standard operating conditions, showing a negligible impact on performance. The validated model is used to investigate typical OSSL structures from the literature, in a virtual high average power regime, and up to the CW regime. It is shown that whenever true CW organic lasing will be realized, significant thermal effects will have to be considered and properly managed.

Optimization of lasing in an inverted-opal titania photonic crystal cavity as an organic solid-state dye-doped laser.

Lasing performance of a dye-doped laser by encapsulating orange fluorescent dye 4-(Dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM) with different concentrations in a highly ordered three-dimensional (3D) inverted-opal titania (TiO2) photonic crystal (PC) microcavity was studied. The lasing threshold and laser quality were improved by optimizing the concentration of the laser dye DCM. When the concentration of DCM is optimized to 10-4 mol/l, the photoluminescence (PL) efficiency of DCM is sufficient to achieve lasing emission and meanwhile no fluorescence quantum quenching occurs. Therefore, the emission spectrum was greatly narrowed and the threshold was significantly improved, which reached 0.8 mJ pulse-1 cm-2. Our findings are promising results toward the realization of fabricating a highly efficient low-threshold organic laser.

Carrier transportation, photoluminescence and lasing characteristics of 1,4-bis[2-[4-[N,N-di(p-tolyl)amino]phenyl]vinyl]benzene: implications for diode-pumped organic solid-state lasers

Two potential schemes were proposed in this work to realize an organic solid laser pumped by electroluminescence emission in an integrated organic light emitting diode (OLED) employing low threshold laser dyes, [1,4-bis[2-[4-[N,N-di(p-tolyl)amino]phenyl]vinyl] benzene (DSB) and DSB doped with 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB), as the hole injection layer (HIL). Using DSB as HIL was found to improve the efficiency of the device, which exhibited peak efficiencies of 9.59 cd A−1 and 6.93 lm W−1. For the system employing DSB doped with DCJTB as HIL, the mobility of the electron transport layer made a large contribution to the realization of a diode-pumped organic solid-state laser. Moreover, the optical characteristics of organic films pumped by a pulsed Nd:YAG laser at 355 nm were also investigated.

Photonic confinement in laterally structured metal-organic microcavities

We investigate the formation of optical modes in organic microcavities with an incorporated perforated silver layer. The metal leads to a formation of Tamm-plasmon-polaritons and thus separates the sample into metal-free or metal-containing areas, supporting different resonances. This mode splitting is exploited to confine photons in elliptic holes and triangular cuts, forming distinctive standing wave patterns showing the strong lateral confinement. A comparison with a Maxwell-Bloch based rate equation model clearly shows the nonlinear transition into the lasing regime. The concentration of the electric field density and inhibition of lateral loss channels in turn decreases the lasing threshold by up to one order of magnitude, to 0.1 nJ. By spectroscopic investigation of such a triangular wedge, we observe the transition from the unperturbed cavity state to a strongly confined complex transversal mode. Such a structured silver layer can be utilized in future for charge carrier injection in an electrically driven organic solid state laser.

Preparation and Characterization of (E)- and (Z)-2-(Biphenyl-4-yl)-1-(4-bromophenyl)-1-phenylethene Isomers

Department of Chemistry, Chung-Ang University, Seoul 156-756, KoreaReceived February 6, 2014, Accepted February 19, 2014Key Words: 2-(Biphenyl-4-yl)-1-(4-bromophenyl)-1-phenylethene, Single-crystal structure, Horner–Wad-sworth–Emmons reactionVarious π-conjugated organic compounds have been ap-plied in a wide range of optoelectronic devices such asorganic field-effect transistors, organic photovoltaic cells,and organic solid-state lasers.

Micro‐LED pumped polymer laser: A discussion of future pump sources for organic lasers

AbstractOptical pumping conditions for organic solid‐state lasers (OSLs) are discussed with particular emphasis on the use of gallium nitride based light‐emitting diodes (LEDs) as pump sources. LEDs operate in a regime where the pump should be optimized for a short rise time and high peak intensity, whereas fall time and overall pulse duration are less important. Lasers pumped with this approach need to have very low thresholds which can now be routinely created using (one‐dimensional) distributed feedback lasers. In this particular case stripe‐shaped excitation with linearly polarized light is beneficial. Arrays of micron‐sized flip‐chip LEDs have been arranged in an appropriate stripe shape and the array dimensions were chosen such that the divergence of LED emission does not cause a loss in peak intensity. These micro‐LED arrays have successfully been used to pump OSLs with thresholds near 300 W/cm2 (∼9 ns rise time, 35 ns pulse duration), paving the way for compact arrays of indirectly electrically pumped OSLs.

DBR-Ag Micro-Cavity Organic Solid-State Lasers

A DBR-Ag mixed organic micro-cavity structure solid-state laser was proposed in this paper. The influences of center wavelength, growth sequence and the cycle number of DBR, and the thickness of Ag mirror and organic light-emitting layer on performance of Ag-DBR mixed organic micro-cavity were investigated by simulation. According to PL characteristics of Alq3:DCM (0.5wt%), an optimal metal Ag-DBR micro-cavity structure was designed, and based on theoretical calculation results, a corresponding micro-cavity devices (glass/DBR/organic layer/Ag mirror) was fabricated. The theoretical simulation and experimental results are in good agreement.

Distributed Feedback Gratings Based on Photo-Polymerization for Organic Solid-State Lasers

A novel preparation method of polymer DFB gratings has developed based on photo-polymerization for organic solid-state lasers. A photopolymer formulation sensitive to ultraviolet light is proposed for fabrication of polymer DFB gratings by spin-coating process. A very low surface relief depth ranging from 12.5 to about 1.0 nm has been demonstrated with a refractive index modulation of about 0.012. The experiment results indicate that the polymer DFB gratings are believed to have promising potentials in the fabrication of low-order DFB organic solid-state lasers.

Continuously tunable organic solid-state DFB laser utilizing molecular reorientation in molecular glasses

We report a facile way for continuously tuning the lasing wavelength of an organic thin-film distributed feedback (DFB) laser after device fabrication by varying the effective refractive index seen by the one-dimension DFB laser structure. Varying the effective refractive indices of the organic gain medium and thus the effective refractive index of a one-dimension DFB laser structure after device fabrication is made possible with reorientation of molecules in a molecular glass at elevated temperatures. Distributions of molecular orientations can be fine controlled by annealing temperatures and times, permitting continuous tuning of optical properties and lasing wavelengths. Molecular reorientation can be conducted after devices are made, thus giving one the freedom to set or tune the lasing wavelength to meet a particular purpose with a common structure.

Lasing and Amplified Spontaneous Emission in a Polymeric Inverse Opal Photonic Crystal Resonating Cavity

We demonstrate the lasing and amplified spontaneous emission in the polymeric inverse opal photonic crystal resonating cavity. The resonating cavity is constructed by sandwiching tert-butyl rhodamine B doped PMMA film with polymeric inverse opal photonic crystals, which work as feedback mirrors. Laser-induced emission experiments reveal lasing or amplified spontaneous emission of the dye molecules in the resonating cavity. Amplified spontaneous emission occurs at the edges of the photonic stop band of the polymeric inverse opal photonic crystal when it partially overlaps with the photoluminescence emission band of the dye molecules. In contrast, lasing action emerges in the resonating cavity when the photonic stop band matches well with the photoluminescence emission band of the dye molecules. Single-mode lasing emission is located at the photonic stop band, indicating the photonic lasing property. The lasing threshold is determined as 4.57 μJ/pulse, and the lasing line width is about 1.0 nm. The present work provides the prospect for constructing low-threshold organic solid-state dye lasers.

Broadly tunable (440–670 nm) solid-state organic laser with disposable capsules

An innovative concept of thin-film organic solid-state laser is proposed, with diffraction-limited output and a broad tuning range covering the visible spectrum under UV optical pumping. The laser beam is tunable over 230 nm, from 440 to 670 nm, with a 3 nm full width at half maximum typical spectral width. The structure consists of a compact fixed bulk optical cavity, a polymeric intracavity etalon for wavelength tuning, as well as five different disposable glass slides coated with a dye-doped polymer film, forming a very simple and low-cost gain medium. The use of interchangeable/disposable “gain capsules” is an alternative solution to photodegradation issues, since gain chips can be replaced without realignment of the cavity. The laser lifetime of a single chip in ambient conditions and without encapsulation was extrapolated to be around 107 pulses at a microjoule energy-per-pulse level.

Nonlinear Optical Properties of a MMA‐Silica Nanohybrid Material Doped with Rhodamine 6G

A novel nanohybrid material based on MMA‐Silica has been synthesized with an organic dye dopant (R6G) to tailor the optical properties. This novel material can be used on several devices such as active laser media for an organic solid state laser, OLEDs, or as a characterization media for new organic dye molecules. Thin films were deposited by dip‐coating and characterized by absorption and reflection UV‐VIS, photoluminescence, SEM, and Z‐scan technique to verify their nonlinear behavior. R6G dye dopant has been used to verify that the nanohybrid matrix does not inhibit its optical properties.

Polarization properties of solid-state organic lasers

The polarization states of lasers are crucial issues both for practical applications and fundamental research. In general, they depend in a combined manner on the properties of the gain material and on the structure of the electromagnetic modes. In this paper, we address this issue in the case of solid-state organic lasers, a technology which enables one to vary independently gain and mode properties. Different kinds of resonators are investigated: in-plane microresonators with Fabry-Perot, square, pentagon, stadium, disk, and kite shapes, and external vertical resonators. The degree of polarization $P$ is measured in each case. It is shown that although transverse electric modes prevail generally ($P$ > 0), the kite-shaped microlaser generates negative values for $P$ (i.e., a flip of the dominant polarization which becomes mostly transverse magnetic polarized). In general, we demonstrate that both the pump polarization and the resonator geometry can be used to tailor the polarization of organic lasers. With this aim in view, we, at last, investigate two other degrees of freedom, namely upon using resonant energy transfer and upon pumping the laser dye to a higher excited state. We then demonstrate that significantly lower $P$ factors can be obtained.

Ab Initio Studies of Triplet-State Properties for Organic Semiconductor Molecules

Triplet–triplet annihilation (TTA) leads to a reduced efficiency of organic light-emitting diodes (OLEDs) at high current densities. Spacial confinement of the triplet excitons, which is mainly dependent on triplet energy differences, can reduce the TTA rate. Therefore, a deliberate choice of the organic semiconductor materials with particular attention to their triplet energies can help to considerably increase the device efficiency. Organic solid-state lasers are, on the other hand, efficiently quenched by singlet–triplet annihilation (STA), which is closely related to the triplet–triplet absorption of the organic semiconductors. To establish a useful set of parameters related to the processes in organic semiconducting devices, we provide theoretical estimates for the triplet energy of 31 organic semiconductor molecules using state-of-the art ab initio quantum chemical methods. For a subset of 22 molecules, the triplet–triplet absorption spectra were calculated as well. We also discuss related features ...

Low threshold amplified spontaneous emission from dye-doped DNA biopolymer

In this study, we investigate the amplified spontaneous emission (ASE) properties and conduct a comparative study for two kinds of dye-doped deoxyribonucleic acid (DNA) biopolymers. The system consists of optical films made of DNA modified by two types of surfactants and doped with a common laser dye rhodamine 6G (Rh6G). The ASE properties of the optical films were characterized by a pulsed Nd:YAG laser. The results show that low threshold of DNA biopolymer can be achieved by the employment of suitable surfactant in the system, resulting from an efficient energy transfer process. Coupled with the fluorescence enhancement exhibited in DNA, this effect can further advance biopolymers toward highly efficient media for lasing applications and organic solid-state lasers.

The photochemistry of the self‐healing chromophore Disperse Orange 11

Recent interest in the self‐healing ability of the laser dye 1‐amino‐2‐methylanthraquinone, Disperse Orange 11, has lead us to investigate the possible alternative mechanisms of action, either intramolecular proton transfer (PT) or twisted intramolecular charge transfer (TICT) formation. AMPAC semiempirical PM3 CI (all single excited configurations) potential energy surfaces searches have been conducted with either reaction mechanism. Based purely on the potential energy surface results, no state, S0, T1, or S1, seems especially likely to be kinetically favorable for PT. The T1 state is favorable thermodynamically for PT. However, the S1 state TICT reaction is both thermodynamically favorable and kinetically preferred over all PT reactions. There is also a favorable T1 TICT reaction, but much slower kinetically on the triplet surface than S1 TICT. The Wentzel–Kramers–Brillouin (WKB) method has been used to ascertain proton tunneling contributions to PT. Even with proton tunneling, S1 TICT is still more highly favored, though proton tunneling could make the T1 PT reaction competitive depending on the rate of intersystem crossing. We also examine spectroscopic properties of PT transfer and TICT reaction path entities in comparison with published experimental evidence. However, this comparison leads to ambiguous findings that suggest that electronic spectral properties alone will not fully clarify the mechanism. Overall, results suggest that the TICT mechanism is the most likely for optical damage and self‐repair for Disperse Orange 11, and might be considered for the damage and repair mechanisms for other organic solid state laser materials. Copyright © 2012 John Wiley & Sons, Ltd.

Analytical study of vertical external-cavity surface-emitting organic lasers

In this paper we report a detailed study of emission dynamics of an organic solid-state laser structure so-called VECSOL standing for Vertical External-Cavity Surface-emitting Organic Laser recently developed in our group. An optical-optical efficiency of 43% and 6.3% was reported for a 4-mm-long cavity incorporating 18- μ m-thick film of Poly(methyl methacrylate) (PMMA) doped with 1 wt.% of Rhodamine 640 when pumped with 7-ns-long and 0.5-ns-long pulses respectively. In order to understand the difference seen in lasing efficiency as a function of different parameters such as cavity length or pump pulse duration, Tang-Statz-deMars cavity rate equations are used to model the emission behavior in a pulsed regime. Based on this model, conversion efficiency could be optimized practically to values as high as 57%. Furthermore, some characteristics of this laser architecture such as lasing lifetime (up to 140 000 pulses at two times above lasing threshold), wavelength tuning (over 40 nm) and the system power scalability with potential operation up to mJ level are investigated.