Dye-doped Holographic Polymer Dispersed Liquid Research Articles

Thermally and optically tunable lasing properties from dye-doped holographic polymer dispersed liquid crystal in capillaries

In this paper, we investigated tunable lasing properties from the dye-doped holographic polymer dispersed liquid crystal (HPDLC) gratings in capillaries with thermal and optical manners. The thermally tunable range of the lasing from the dye-doped HPDLC reached 8.60 nm with the temperature ranging from 23 °C to 50 °C. The optically tunable laser emission was achieved by doping azo-dye in HPDLC. The transition of azo-dye from trans- to cis-state could induce the reorientation of LC molecules after UV light irradiation, which resulted in the variation of refractive index contrast of LC-rich/polymer-rich layer in HPDLC. Experimentally, the emission wavelength of lasing showed a blueshift (about 2 nm) coupled with decreasing output intensities. The tunable laser based on HPDLC may enable more applications in laser displays, optical communication, biosensors, etc.

High conversion efficiency distributed feedback laser from a dye-doped holographic transmission grating

A high conversion efficiency distributed feedback (DFB) laser from a dye-doped holographic polymer dispersed liquid crystal (HPDLC) transmission grating structure was reported. The alignment polyimide (PI) films were used to control the orientation of the phase separated liquid crystals (LCs) to increase the refractive index difference between the LC and the polymer, so it can provide better light feedback. The lasing wavelength located at 645.8 nm near the maximum of the amplified spontaneous emission (ASE) spectrum with the lowest threshold 0.97 and the highest conversion efficiency 1.6% was obtained. The laser performance under electric field were also investigated and illustrated. The simple configuration, one-step fabrication organic dye laser shows the potential to realize ultra-low cost plastic lasers.

Lasing properties from dye-doped holographic polymer dispersed liquid crystal confined in two-dimensional cylindrical geometry

In this paper, we investigate the lasing behavior of holographic polymer dispersed liquid crystals (H-PDLCs) filled in capillary tubes (CTs). The emission properties from CTs with various core diameters are explored experimentally. The experimental results show that the smallest threshold is 19.4 μJ/pulse in CTs III (300 μm) corresponding to the largest FWHM 0.42 nm. The minimum FWHM is 0.29 nm in CTs I (75 μm) corresponding to largest threshold 31.5 μJ/pulse. According to experimental results and theoretical analysis, the different lasing behaviors from various core diameters of CTs are mainly due to the effect of phase separation between LC-rich and polymer-rich area during exposure. The temperature effects on lasing properties of H-PDLC in CTs were also investigated. Our work verifies the possibility to achieve miniature laser devices in cylindrical confinement structures, such as CT, hollow-fiber or photonic crystal fiber, and extends the applicable scope of H-PDLC.

Anisotropic waveguide theory for electrically tunable distributed feedback laser from dye-doped holographic polymer dispersed liquid crystal

Anisotropic waveguide theory is developed for electrically tunable distributed feedback (DFB) laser from dye-doped holographic polymer dispersed liquid crystal (HPDLC) grating. The period grating structure, optical anisotropy of the liquid crystal (LC) and practical light propagation path in the HPDLC have been considered. The emitted lasing wavelength is deduced on basis of the dielectric anisotropy of the LC, transverse-magnetic (TM) light wave propagation in the core layer and DFB laser theory. An experimental method to determine the tilt angle of the LC and the lasing behaviours under different electric fields are used to verify the validity of the anisotropic numerical analysis. The results show that a more accurate agreement between the theoretical calculations and the experimental data is achieved. The anisotropic numerical analysis presented here is very useful when designing and optimising tunable lasers for optical communications and integrated optics.

Low threshold of distributed feedback lasers based on scaffolding morphologic holographic polymer dispersed liquid crystal gratings: reduced losses through Forster transfer

The threshold of distributed feedback (DFB) lasing from dye-doped holographic polymer dispersed liquid crystal (HPDLC) gratings was reduced using a guest–host (G–H) system. Different doping concentrations of the guest emitter 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM) in the host dye 1,3,5,7,8-pentamethyl-2,6-diethylpyrromethene-difluoroborate (PM567) were dispersed in the HPDLC transmission gratings. DFB lasing was observed in the pure host, the pure guest and in the G–H system. With the increase in doping concentration of the guest, the gain spectrum was redshifted. Through effective Forster energy transfer, we found that the lasing threshold was lowered to 1.35 μJ/pulse, which reduced by factor 2 compared to that without energy transfer process. This effect is attributed to the suppression of self-absorption at the lasing wavelength.

Wavelength tunable properties for distributed feedback lasing from dye-doped holographic polymer dispersed liquid crystal transmission grating

In this paper, we study the wavelength tunable properties for distributed-feedback lasing from 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM) dye-doped holographic polymer dispersed liquid crystal grating. By preparing and pumping the DCM-doped HPDLC gratings with various grating spacings, we depict the tuning curve of the distributed-feedback lasing and confirm that only in a range from 574 nm to 685 nm, the lasing action can be observed. Then, we adjust the temperature of the sample and measure the lasing spectrum from the DCM-doped holographic polymer dispersed liquid crystal grating with a grating period of 610nm. There is an obvious 4.9 nm blueshift from 627.9 nm to 623 nm for the lasing wavelength with the temperature increasing from 20℃ to 65℃.

Organic dual-wavelength distributed feedback laser empowered by dye-doped holography

An organic dual-wavelength distributed feedback (DFB) laser empowered by a dye-doped holographic polymer dispersed liquid crystal (HPDLC) grating is reported for the first time. The dual-wavelength laser operates at 586.6 nm and 670.2 nm simultaneously in one laser beam via the seventh and eighth Bragg orders of a one dimensional (1D) HPDLC grating with a special period. We theoretically and experimentally demonstrate the mechanism of our dual-wavelength DFB laser and investigate the threshold and spectral properties of the output laser. Our organic dual-wavelength DFB laser shows the advantages of simple configuration, one-step fabrication, cost-effectiveness and the potential application to be integrated in all optical networks.

Distributed-feedback lasing from dye-doped holographic polymer dispersed liquid crystal transmission grating

In this paper,we report the fabrication of dye-doped holographic polymer dispersed liquid crystal(HPDLC) transmission grating and the property of distributed-feedback lasing from dye-doped HPDLC transmission grating. Under the excitation of a frequency-doubled Nd:yttrium-aluminum-garnet laser operating at a wavelength of 532 nm, optically pumped lasing with narrow linewidth and low threshold was observed from a DCM dye-doped HPDLC transmission grating with the grating period of 586 nm. The results showed that the emitted lasing peak centered at about 603 nm with a full width at half maximum (FWHM) of only 1.4 nm, and the threshold pumping intensity was about 17.3 μJ, which is evidently lower than the previously reported values.

High contrast switching of distributed-feedback lasing in dye-doped H-PDLC transmission grating structures

Electrically switched distributed-feedback (DFB) lasing action is presented in a Pyrromethene 580 lasing dye-doped holographic polymer dispersed liquid crystal (H-PDLC) transmission grating structure. This design, when compared with the previously utilized H-PDLC reflection grating structure, has the advantage of a greatly enlarged gain length (10 mm) and a low concentration of liquid crystal (20%) while maintaining sufficient refractive index modulation. The experimental results demonstrate that the emitted laser bandwidth (~5 nm) can be obtained with a pump energy threshold of ~0.3 mJ at three different wavelengths, 561 nm, 569 nm and 592 nm, corresponding to three different grating spacings. The near- and far-field measurements have shown a high directionality of the lasing output. The lasing can be electrically switched off by an applied field of 30V/mum. The temporal, spectral, and output/input properties of the laser output are also presented.

Light amplification by dye-doped holographic polymer dispersed liquid crystals

In this letter we report a “one-step” fabrication technique of an optical active organic photonic band gap (PBG) structure allowing the onset of the amplification spontaneous emission effect and narrowing of the corresponding band. This result has been achieved through the addition of the dye rhodamine 6G to a standard holographic polymer dispersed liquid crystal pre-polymer mixture. The effects of the dye addition on the optical properties of the polymerized PBG structure have been analyzed. The spectra emitted by this optically active periodic structure have been studied as a function of the excitation energy.