Tunable Visible Laser Research Articles

1283-1460 nm continuously tunable, watt-level bismuth-doped phosphosilicate fiber laser and its frequency doubling to a visible laser.

We report, to the best of our knowledge, the first demonstration of an O + E-band tunable watt-level bismuth-doped phosphosilicate fiber laser and its frequency doubling to tunable red laser. Benefiting from the two types of bismuth active centers associated with silicon and phosphorus introduced in one fiber, an ultrabroad gain is available in the designed low-water-peak bismuth-doped phosphosilicate fiber (Bi-PSF) pumped by a self-made 1239 nm Raman fiber laser. The high-efficiency tunable lasing is achieved with a maximum output power of 1.705 W around 1320 nm and a slope efficiency of 33.0%. The wavelength can be continuously tuned from 1283 to 1460 nm over a 177 nm spectral range, almost covering the whole O+E-bands. We further employ a polarization beam splitter in the cavity to output an O + E-band linear-polarization laser for second-harmonic generation by a designed multi-period MgO2:PPLN crystal, and a 650-690-nm tunable visible laser is correspondingly obtained. Such an O+E-wideband tunable high-power laser and the SHG red laser may have great potential in the all-band optical communications, biophotonics, and spectroscopy.

Nanophotonic detector array to enable direct thermal infrared vision.

Detection of infrared (IR) photons in a room-temperature IR camera is carried out by a two-dimensional array of microbolometer pixels which exhibit temperature-sensitive resistivity. When IR light coming from the far-field is focused onto this array, microbolometer pixels are heated up in proportion to the temperatures of the far-field objects. The resulting resistivity change of each pixel is measured via on-chip electronic readout circuit followed by analog to digital (A/D) conversion, image processing, and presentation of the final IR image on a separate information display screen. In this work, we introduce a new nanophotonic detector as a minimalist alternative to microbolometer such that the final IR image can be presented without using the components required for A/D conversion, image processing and display. In our design, the detector array is illuminated with visible laser light and the reflected light itself carries the IR image which can be directly viewed. We numerically demonstrate this functionality using a resonant waveguide grating structure made of typical materials such as silicon carbide, silicon nitride, and silica for which lithography techniques are well-developed. We clarify the requirements to tackle the issues of fabrication nonuniformities and temperature drifts in the detector array. We envision a potential near-eye display device for direct IR vision based on timely use of diffractive optical waveguides in augmented reality headsets and tunable visible laser sources. Our work indicates a way to achieve thermal IR vision for suitable use cases with lower cost, smaller form factor, and reduced power consumption compared to the existing thermal IR cameras.

Tailoring the efficiency and spectrum of a green random laser generated by frequency doubling of random fiber lasers.

Frequency doubling of random fiber lasers could provide an effective way to realize visible random lasing with the spectrum filled with random frequencies. In this paper, we make a comprehensive study on the efficiency and spectral manipulation of a green random laser generated by frequency doubling of an ytterbium-doped random fiber laser (YRFL). To tailor the efficiency of green random lasing generation, the ytterbium-doped random fiber lasing is filtered at different spectral positions, and then amplified to watt-level to serve as the fundamental laser source for frequency doubling in a periodically poled lithium niobate (PPLN) crystal. We found that by selecting different spectral components of ytterbium-doped random fiber lasing, the temporal intensity fluctuations of the filtered radiations vary dramatically, which plays an important role in enhancing the efficiency of frequency doubling. By fixing the filtering radiation wavelength at 1064.5 nm and tuning the central wavelength of YRFL, we experimentally demonstrate that, compared to the filtered radiation in the center of the spectrum, the efficiency of frequency doubling can be nearly doubled by utilizing the filtered ytterbium-doped random fiber lasing in the wings of the spectrum. As a result, the conversion efficiency of the generated green random laser at 532.25 nm can be more than 11% when the input power of the polarized 1064.5 nm fundamental light is 2.85W. For spectral manipulation, we realize a spectral tunable green random laser in the range of 529.9 nm to 537.3 nm with >100 mW output power for the first time by tuning the wavelength of YRFL and the temperature of PPLN simultaneously. The system can be naturally modified to simultaneously realize the efficiency enhancement and wavelength tuning, thus providing a new route to generate high efficiency and tunable visible random laser via frequency doubling that are potentially useful for imaging, sensing and visible light communication applications.

Discretely Tunable Multiwavelength Visible Laser Based on Cascaded Frequency Conversion Processes

We demonstrate a discretely tunable multiwavelength visible laser through second harmonic generation (SHG) and sum frequency generation (SFG) of multiorder Stokes lasers generated from an external Raman laser oscillator. The Raman laser oscillator, driven by a 1064 nm laser with an energy of 120 mJ, is based on a cascade of Ba(NO3)2 and two axial orthogonal KGd(WO4)2 crystals. Through adjusting the angle of the SHG/SFG crystal, we obtain 16 visible wavelengths with a wide range from 579.5–658.4 nm. In addition, we investigate the output energy and conversion efficiency of the resulting laser with various phase-matching angles. We show that the maximum energy of the visible laser is 8.87 mJ with five wavelengths, and the corresponding total conversion efficiency is 7.4%. These experimental results demonstrate a practical and effective method of generating a discretely tunable multiwavelength visible laser.

Laser wavelength metrology with low-finesse etalons and Bayer filters

We present a wavelength meter with picometer-scale resolution based on etaloning effects of inexpensive glass slides and the built-in color filters of a consumer grade CMOS camera. After calibrating the device to a commercial meter, we tested the device's calibration stability using two tunable visible lasers for a period of over 16 days. The wavelength error over that entire period has a standard deviation of 5.29 parts per million (ppm) about a most probable error of 0.90 ppm. Within 24 hours of calibration, this improves to 0.04 ppm with a standard deviation of 3.94 ppm.

Deep Red Tunability and Output Power Performances of Visible Laser Emission in a Pr:Ba(Y1-xLux)2F8 Single Crystal.

The demand for tunable visible laser sources with high power and high beam quality, for application ranging from metrology to remote sensing, is constantly increasing. In this work, we report on the details of crystal growth, via the Czochralski method, and laser characterization of a Pr-doped Ba(YLu)F (BYLF) single crystal, which is a promising candidate for fulfilling these requirements, both in terms of tunability and high-power capabilities. We measured for the first time the laser tunability curve in the deep red region obtaining a continuous range of 17 nm. The laser emission of the three main Pr lines in the visible (orange, red, and deep red) was tested under increased pump power with respect to previous studies on this material, demonstrating output powers of more than 360 mW and no thermal rolloff, up to 1.9 W of absorbed power.

Excitability of high-energy ultraviolet radiation for Dy3+ in antimony phosphate glasses

Abstract Dy3+ doped antimony phosphate (ZASP) glasses are synthesized and the specificity of the luminescence behavior is demonstrated. Different from the conventional long-wave ultraviolet (UVA) exciting cases, the excitable area of Dy3+ doped ZASP glasses is extended to high-energy ultraviolet radiation including medium-wave ultraviolet (UVB) and short-wave ultraviolet (UVC) spectral regions. The quantum efficiency for 4F9/2 level of Dy3+ in low- and medium-concentration Dy2O3 doping cases reaches 95.0 % and 66.7 %, respectively, confirming the emission effectiveness from Dy3+ in ZASP glasses. The values of energy-transfer probability (P) have obvious difference while using 340 nm and 540 nm as monitoring wavelengths, so asthe energy-transfer efficiencies (η), which are related to the energy-transfer processes from discrepant Sb3+ donors to Dy3+ acceptors, were in-equivalent. The effective excitability of high-energy ultraviolet radiation illustrates that Dy3+ doped ZASP glasses are a promising candidate in developing visible light sources, display devices and tunable visible lasers.

Inkjet-printed vertically emitting solid-state organic lasers

In this paper, we show that Inkjet Printing can be successfully applied to external-cavity vertically emitting thin-film organic lasers and can be used to generate a diffraction-limited output beam with an output energy as high as 33.6 μJ with a slope efficiency S of 34%. Laser emission shows to be continuously tunable from 570 to 670 nm using an intracavity polymer-based Fabry-Perot etalon. High-optical quality films with several μm thicknesses are realized, thanks to ink-jet printing. We introduce a new optical material where EMD6415 commercial ink constitutes the optical host matrix and exhibits a refractive index of 1.5 and an absorption coefficient of 0.66 cm−1 at 550–680 nm. Standard laser dyes like Pyrromethene 597 and Rhodamine 640 are incorporated in solution to the EMD6415 ink. Such large size “printed pixels” of 50 mm2 present uniform and flat surfaces, with roughness measured as low as 1.5 nm in different locations of a 50 μm × 50 μm AFM scan. Finally, as the gain capsules fabricated by Inkjet printing are simple and do not incorporate any tuning or cavity element, they are simple to make, have a negligible fabrication cost, and can be used as fully disposable items. This work opens the way towards the fabrication of really low-cost tunable visible lasers with an affordable technology that has the potential to be widely disseminated.

A series of color tunable yellow–orange–red-emitting SrWO4:RE (Sm3+, Eu3+–Sm3+) phosphor for near ultraviolet and blue light-based warm white light emitting diodes

A series of wide-range-tunable light emissive SrWO4:Sm3+, SrWO4:Sm3+,Eu3+ phosphors were synthesized via the simple co-precipitation method. The charge compensation can greatly improve SrWO4: Sm3+ phosphors luminous intensity. The critical distance, ηT and energy transfer mechanism of SrWO4:0.01Sm3+,0.12Eu3+ were studied. These obtained phosphors exhibit a high luminous efficiency, purity and lower color temperature of the comfortable warm white LEDs. Hues varying have been generated by appropriately tuning the Sm3+ ions concentration, excitation wavelength or Sm3+, Eu3+ co-doping, which have the color tunable wide gamut light covering the yellow–green, greenish-yellow, yellow, yellow orange, orange, reddish orange and red chromaticity region. In particular, SrWO4:0.01Sm3+,0.12Eu3+ phosphors excited at 404 and 480 nm have higher color saturation than commercially available Y2O2S:Eu3+ red phosphor. These phosphors can be excited efficiently using commercial ultraviolet, blue laser diodes and LEDs, and can be used for developing new color light sources, fluorescent display devices, ultraviolet-sensors and tunable visible lasers.

Spectroscopic properties and external quantum yield of Sm3+ doped germanotellurite glasses

Sm3+ doped germanotellurite glasses (NZPGT) with maximum phonon energy of 793cm−1 have been prepared and characterized. Judd–Ofelt parameters Ωt (t=2, 4, 6) have been calculated to be 3.52×10−20, 4.70×10−20 and 1.90×10−20cm2, respectively. Large value of Ω2 indicates a high asymmetry and covalent environment around Sm3+ in the glass system. The maximum stimulated emission cross-section of the dominant transition 4G5/2→6H9/2 peaking at 645.0nm was derived to be 10.00×10−22cm2, predicting that the red fluorescence emission can be efficiently extracted from the optical glasses. The internal quantum efficiency and external quantum yield of 0.4wt% Sm2O3 doped NZPGT glasses were deduced to be 82.5% and 6.0%, respectively. The results demonstrate that Sm3+ doped NZPGT glasses are a potential candidate for developing tunable visible lasers, compact light sources and solid-state display devices.

Luminescence Properties of Dy3+ and Sm3+: Potassium Lithium Borate Glass

The present paper describes the spectral properties of Sm3+ (0.4 mol%) and Dy3+ (0.4 mol%) ions-doped 20Li2O–10K2O–70B2O3 glasses. X-ray diffraction method was use to confirm the amorphous phase of samples. The physical properties have been determined based on UV absorption spectra. The hypersensitive transition of Dy3+ and Sm3+ is found due to transition of (6F11/2,6H9/2) and (6F7/2), respectively. The emission bands of Dy3+: glass has shown around 572 nm, 612 nm and 646 nm; these emissions are attributed to the transitions of 4F9/2 ®6H15/2 (yellow), 4F9/2 - 6H13/2 (red) and 4F9/2 -6H11/2 (red). With regard to Sm3+: glass has three emission bands those have been generated from 4G5/2 ® 6H5/2 (616 nm), 4G5/2 ® 6H 7/2 (660 nm) and 4G5/2 ® 6H9/2 (719 nm) transitions. The current results promise several applications in optical fields such as UV-sensor, developing new color light sources and tunable visible lasers.

White upconversion luminescence generation from Ho3+ singly doped chalcohalide glasses

Bright white light which compose of blue, green and red emission bands from Ho3+ single doped Ge–Ga–S–CsCl (CsBr) chalcohalide glasses under 900nm infrared laser excitation were observed and investigated. The calculated color coordinates proved that the light were close to the natural sunlight. The low phonon energy of the local surrounding of Ho3+ ions and short ultra-violet cut-off edge resulted in the strong blue emission, as well as the enhanced green and red upconversion luminescence. It was also found that color coordinates of these white lights were independent on the excitation intensity. The result indicated that Ho3+ ions singly doped chalcohalide glass can be promising candidate for white light source, 3-dimensional display or color tunable visible laser.

High-efficiency fluorescence radiation of Dy3+ in alkaline earth borate glasses

Dy3+-doped alkaline-earth borate glasses (LKZBSB) with high quantum yield and multifarious emission channels have been fabricated and efficient warm yellowish-white fluorescence is presented under UV light excitation. Judd–Ofelt parameters Ω2=5.36×10−20cm2, Ω4=1.46×10−20cm2 and Ω6=1.95×10−20cm2 indicate a high asymmetrical and covalent environment in the optical glasses. The maximum stimulated emission cross-sections σem-max corresponding to the 4F9/2→6H15/2, 4F9/2→6H13/2, 4F9/2→6H11/2 and 4F9/2→(6H9/2, 6F11/2) transitions are derived to be 2.64×10−22, 20.07×10−22, 3.45×10−22 and 9.31×10−22cm2, respectively, and the relevant spontaneous emission probabilities Arad are 174.08, 616.07, 68.95 and 87.10s−1. Quantitative characterization reveals that Dy3+-doped LKZBSB glasses exhibit a quantum yield as high as 16.65%, confirming that the effectiveness of the warm yellowish-white luminescence in Dy3+-doped LKZBSB glasses. Multifarious emission channels and high quantum yield illustrate the great advantages of Dy3+-doped LKZBSB glasses in developing fiber-lighting sources, display devices, tunable visible lasers, and optical signal amplifiers.

All-polymer organic semiconductor laser chips: Parallel fabrication and encapsulation

Organic semiconductor lasers are of particular interest as tunable visible laser light sources. For bringing those to market encapsulation is needed to ensure practicable lifetimes. Additionally, fabrication technologies suitable for mass production must be used. We introduce all-polymer chips comprising encapsulated distributed feedback organic semiconductor lasers. Several chips are fabricated in parallel by thermal nanoimprint of the feedback grating on 4″ wafer scale out of poly(methyl methacrylate) (PMMA) and cyclic olefin copolymer (COC). The lasers consisting of the organic semiconductor tris(8-hydroxyquinoline) aluminum (Alq3) doped with the laser dye 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyril)-4H-pyrane (DCM) are hermetically sealed by thermally bonding a polymer lid. The organic thin film is placed in a basin within the substrate and is not in direct contact to the lid. Thus, the spectral properties of the lasers are unmodified in comparison to unencapsulated lasers. Grating periods of 378 nm to 428 nm in steps of 10 nm result in lasing at wavelengths of 622 nm to 685 nm. The operational lifetime of the lasers expressed in number of pulses is improved 11-fold (PMMA) and 3-fold (COC) in comparison to unencapsulated PMMA devices.

Tunable green-red luminescence in Ho 3+/Yb 3+/Ce 3+: YF 3 nanocrystals embedded transparent glass ceramics

The Ho 3+/Yb 3+/Ce 3+:YF 3 nanocrystals embedded transparent oxyfluoride glass ceramics were successfully synthesized and the emission spectra have been measured. We changed the doped concentrations of ion Ce 3+ in the glass ceramics and unexpectedly found that the different concentrations brought forth different luminescence wavelengths, a tunable luminescence wave band from green to red, which might be useful to the tunable visible laser or display applications. In addition, excitated with wavelength 975 nm LD, the transitions of Ho 3+: 5G 4 → 5I 8 at 390 nm, 5G 5 → 5I 8 at 420 nm and 5F 3 → 5I 8 at wavelength 490 nm were observed in the glass ceramic GCCe0, while in samples GCCeJ(J=1,3,5,8), the three peaks disappeared.

A proposal of a high‐resolution tunable visible laser source generation

AbstractA new system of a highly tunable visible laser source using a Gaussian pulse propagating within a nonlinear microring resonator system is proposed. Several Gaussian pulses with different center wavelengths are investigated using the designed system. The obtained results have shown that the very fine tuning wavelengths covering the visible laser wavelengths can be generated. With the very sharp peak and broad spectrum, for instance, when the Gaussian input pulse with the center wavelength at 700 nm, the spectral width of 20 pm is obtained. The interesting aspect is that the increasing in microscopic recording pen (i.e. peak) can be used to increase the imaging resolution, where the multicolor imaging, especially for multicolor bio‐cell microscopy is the target. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 406–408, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24903

Microchannel fabrication in silica glass by femtosecond laser pulses with different central wavelengths

A newly developed tunable visible femtosecond laser source was used to fabricate microchannels in silica glass. For comparison, femtosecond laser pulses from a Ti-sapphire laser at 800 nm as well as from a femtosecond optical parametric amplifier at 1.3 µm were also employed to fabricate microchannels. We found that it is much more efficient to drill micro-channels using the visible pulses because of their lower damage threshold. The quality of the cross section of the microchannel is also better with this visible femtosecond laser source because of the high beam quality of the visible pulses.

Optical absorption and photoluminescence in Sm 3+- and Eu 3+-doped rare-earth borate glasses

Sm 3+- and Eu 3+-doped rare-earth borate glasses (Li 2O–BaO–La 2O 3–B 2O 3) have been fabricated and characterized optically. The density, refractive index, optical absorption, Judd-Ofelt parameters, and spontaneous transition probabilities have been measured, calculated and analyzed. Sm 3+ and Eu 3+ emit intense reddish-orange and red lights under blue and UV light excitations, respectively. In Sm 3+ and Eu 3+ co-doped glasses, the excitation wavelength range of Eu 3+ emission is broadened owing to the energy transfer from Sm 3+ to Eu 3+. This broadening makes the Ar + 488 nm wavelength laser a powerful excitation source for Eu 3+ fluorescence. The rare-earth doped glasses with various visible emissions are useful for developing new color light sources, fluorescent display devices, UV-sensor and tunable visible lasers.

Intense visible fluorescence and energy transfer in Dy 3+, Tb 3+, Sm 3+ and Eu 3+ doped rare-earth borate glasses

Tb 3+/Dy 3+ and Eu 3+/Sm 3+ doped rare-earth borate glasses have been synthesized and characterized. Under UV excitation, Dy 3+, Tb 3+, Sm 3+ and Eu 3+ emit intense yellowish white, green, reddish orange and red lights, respectively. In Tb 3+/Dy 3+ co-doped glasses, the enhancement of Tb 3+ green emission is observed, and the sensitization is related to the efficient energy transfer from Dy 3+ to Tb 3+. In Eu 3+/Sm 3+ co-doped glasses, the excitation wavelength range of Eu 3+ emission is broadened owing to the energy transfer from Sm 3+ to Eu 3+. This broadening makes the Ar + 488 nm wavelength laser a powerful excitation source for Eu 3+ fluorescence. The rare-earth doped glasses with various visible emissions are useful for developing new color light sources, fluorescent display devices, UV-sensor and tunable visible lasers.

Resonance enhanced multiphoton dissociation of polycyclic aromatic hydrocarbons cations in an RF ion trap

We present a novel method for recording the absorption spectra of cations of non-volatile molecules using resonance enhanced multiphoton dissociation of trapped ions. Ions are produced through a 2-laser desorption/ionization process in an RF ion trap mass-spectrometer. A third tunable visible laser induces fragmentation of the trapped ions with a yield dependent on the absorption cross-sections of the ions. Using this method we have recorded the visible absorption spectrum of two PAH isomers, phenanthrene and anthracene.