Tapered diode lasers and laser modules near 635nm with efficient fiber coupling for flying-spot display applications

Flying-spot displays require light sources in the red, green and blue with a high optical output power and nearly diffraction limited beams. In this paper we present experimental results of red-emitting, AlGaInP based, tapered diode lasers and their integration into diode laser modules. The laser modules emit a collimated, almost diffraction limited beam with an optical output power as high as 1W at a wavelength close to 635 nm. The tapered laser chips were designed with emphasis on achieving a good beam quality in vertical and lateral directions of a collimated beam. To test the suitability for flying-spot display applications, we performed fiber coupling experiments with a low mode number optical fiber with an etendue as low as 6 × 10^?6 mm² sr. A maximum transmission of 70% of the launched power behind the uncoated fiber as well as a usable power in excess of 580mW were measured.     

Miniaturized highly brilliant diode laser modules for future display applications

We demonstrate diode laser modules with high spectral radiance larger than 1 GW/cm²/sr/nm in the visible spectral range. These highly brilliant laser light sources enable the development of next-generation 3D displays. About 1W output power from small-sized modules was achieved at 635 nm by direct diode laser emission and at 530 nm using single pass second harmonic generation (SHG) of a highly brilliant near-infrared laser diode.     

Watt-level continuous-wave and passively Q-switched red lasers pumped by a single blue laser diode

Praseodymium-ion-doped gain materials have the superiority of lasing at various visible wavelengths directly.Simple and compact visible lasers are booming with the development of blue laser diodes in recent years. In this Letter, we demonstrate the watt-level red laser with a single blue laser diode and Pr:YLiF_4 crystal. On this basis,the passively Q-switched pulse lasers are obtained with monolayer graphene and Co:ZnO thin film as the Q-switchers in the visible range.     

可调色红光有机电致发光器件

介绍了具有可调节发光光谱的高效红光有机发光二极管(OLED)器件,利用具有高三重态能量的9.9-螺二芴二苯基氧化磷(SPPO1)作为发光层的主体材料及空穴阻挡层,二(1-苯基异喹啉)(乙酰丙酮)合铱(III) (Ir(piq)2(acac))作为客体发光材料,在发光层内SPPO1的能量分别由福斯特和迪克斯特传递到Ir(piq)2(acac)的单重态和三重态从而发出红色磷光,通过调节磷光客体材料的比例得到最优器件结构,从而得到具有较好发光效率和发光亮度并可调节色纯的有机发光二极管器件。     

可调色红光有机电致发光器件

介绍了具有可调节发光光谱的高效红光有机发光二极管(OLED)器件,利用具有高三重态能量的9.9-螺二芴二苯基氧化磷(SPPO1)作为发光层的主体材料及空穴阻挡层,二(1-苯基异喹啉)(乙酰丙酮)合铱(III) (Ir(piq)2(acac))作为客体发光材料,在发光层内SPPO1的能量分别由福斯特和迪克斯特传递到Ir(piq)2(acac)的单重态和三重态从而发出红色磷光,通过调节磷光客体材料的比例得到最优器件结构,从而得到具有较好发光效率和发光亮度并可调节色纯的有机发光二极管器件。     

Design and applications of discrete mode Fabry-Perot diode lasers

We describe how the multimode spectrum of a Fabry-Perot diode laser can be tailored using a non-periodic patterning of the cavity effective index. The cavity geometry is obtained from the solution of an inverse problem based on a perturbative calculation of the threshold gain of the longitudinal modes of the cavity. Experimental measurements are presented that demonstrate an all-optical memory element based on the injection locking bistability of a two-mode device. We also demonstrate passive harmonic mode-locking of a device designed to support a comb of six modes. Near-transform limited pulsed output with 2 ps pulse duration at 100 GHz repetition rate was obtained. Prospects for the extension of our approach to locking of larger numbers of modes over wider bandwidths are discussed. Similarities between the effective index profiles found in these devices and those of related devices and grating structures are also highlighted.     

High-brightness diode lasers

The basic concepts and some modelling aspects of high-brightness semiconductor lasers are reviewed. The technology of lasers with a tapered gain-region is described. They provide the highest brightness of a semiconductor source with continuous wave emission in the visible and near infrared spectral range. Experimental results are presented for tapered lasers emitting at 735 nm and 808 nm. Output powers of 3 W were achieved in nearly diffraction limited beams. To cite this article: H. Wenzel et al., C. R. Physique 4 (2003).     

Rate equation approach for diode lasers

The light output and the electron density within the active layer of a semiconductor laser have been calculated from the steady state solution of a rate equation approach. The assumed rate equation model takes into account the spontaneous emission into the lasing modes. Simple analytical approximation formulae have been found under the assumption of a power-law dependence between optical gaing and electron densityn (g ∞n′). The approximations are compared with numerical results from the rate equations. With the exception of a small region near the lasing threshold good agreement has been found. The theoretical results are compared with experimentally measured light outputs from single and double heterostructure lasers. From the comparison below threshold the power law exponent/may be evaluated. The comparison at threshold suggests that the spontaneous emission term decreases at threshold. This decrease is in agreement with experimentally measured changes of the emission bandwidth at threshold.     

Interference-filter-stabilized external-cavity diode lasers

We have developed external cavity diode lasers, where the wavelength selection is assured by a low loss interference filter instead of the common diffraction grating. The filter allows a linear cavity design reducing the sensitivity of the wavelength and the external cavity feedback against misalignment. By separating the feedback and wavelength selection functions, both can be optimized independently leading to an increased tunability of the laser. The design is employed for the generation of laser light at 698, 780 and 852 nm. Its characteristics make it a well suited candidate for space-born lasers.     

Finite-element thermal model for buried-heterostructure diode lasers

First results of our new finite-element modelling of thermal properties of GaAs/(AlGa)As buried-heterostructure (BH) lasers are reported. The calculus procedure is very efficient, so we have used a standard IBM PC/XT microcomputer. For the stripe active-region width of 1 m, the thermal resistance of the laser was determined to be about 70 KW^-1, whereas its electrical resistance was about 6 ohms. To the best of our knowledge, isothermal lines within BH lasers have been obtained for the first time. The isothermal configuration enables us to analyse heat-spreading phenomena in BH lasers, which makes possible thermal optimization of the laser construction.As the first application of the model, the relative influence of the oxide layer thickness on the laser thermal resistance was examined. Because of relatively large lateral dimensions of the laser crystal as compared to the active region, this influence is often neglected, whereas our detailed calculations reveal its importance. An increase in this thickness from 0.1 m to 0.5 m is followed by over 15% increase in the laser thermal resistance.     

High-power broad-area diode lasers for laser cooling

Received: 1 April 1996/Revised version: 24 September 1996     

Stable diode lasers for hydrogen precision spectroscopy

We report on an external cavity diode laser at 972 nmstabilized to a mid-plane mounted Fabry-Perot (FP) resonator with afinesse of 400000. The 0.5 Hz optical beat note line width betweentwo similar lasers (Allan deviation 2 × 10^-15) is limitedby thermal noise properties of two independent FP resonators. Thelong term drift of the FP resonator and mirror substrates made fromUltra-Low-Expansion glass (ULE) is small and can be well predictedon time intervals up to many hours if the resonator is stabilized atthe zero thermal expansion temperature T_c. Using a Peltierelement in a vacuum chamber for temperature stabilization allowsstabilization of the FP cavity to T_c which is usually below theroom temperature. Beat note measurements with a femtosecond opticalfrequency comb referenced to a H-maser during 15 hours have shown awell defined linear drift of the FP resonance frequency of about 60 mHz/s with residual frequency excursions of less than ±20 Hz.     

Efficiency control of organic light-emitting diode for high contrast ratio performance in active matrix display applications

We demonstrate the possibility of controlling organic light-emitting diodes (OLEDs) efficiency with an optimized hole-delay layer (HDL) in order to achieve very high contrast ratio needed for active matrix display applications. No triplet exciton confinement structure and a molybdenum trioxide (MoO₃) HDL at ITO/hole transport layer interface were used for a careful placing and adjusting of the exciton recombination zone. An optimized thickness of 50 nm thick MoO₃ allows to cut off the efficiency at the black level of active matrix driving mode while it gets greater at higher luminance at high current density region over 20 mA/cm² compared to conventional device. Our suggested efficiency control way is believed to be very useful to future active matrix OLED displays.     

Intra-cavity spectroscopy with diode lasers

A multi-mode diode laser with an external cavity is studied experimentally and theoretically for its application to intra-cavity spectroscopy. One facet of a typical Ga_0.89Al_0.11As laser diode was antireflection-coated by deposition of HfO₂ such that 10^–3 residual reflectivity was left over. This diode was placed in an external optical cavity. The emission spectrum of this diode laser is highly sensitive to any frequency-dependent loss in the cavity, and the detectivity of such a loss grows with the pump rate. Even close to threshold, the absorption at 780 nm of Rb atoms with a density of 5×10¹⁰ cm^–3 has been detected. An adequate model for diode lasers based on rate equations and including frequency-dependent gain saturation is developed and applied to the calculations of output spectra. The sensitivity of these spectra to intra-cavity absorption is determined by the overall cavity loss — which is rather high — and the fraction of spontaneous emission in the total emission, in contrast with dye lasers where it is limited by nonlinear mode coupling. Various criteria for the sensitivity are suggested. The smallest detectable absorption with a perfectly antireflection-coated laser is 10^–6 cm^–1. Improvement of the characteristics of the laser diode would increase the sensitivity.     

Heterostructure with extended optical waveguide for diode lasers

The thickness and composition of diode heterolaser layers are optimized with respect to the ratio of the optical beam width d to the optical confinement factor Γ. The stability of the vertical near field distribution and the most important waveguide parameters to static changes and dynamic variations of the refractive indices of heterostructure layers is tested in the laser operation mode.     

Compact phase-lock loop for external cavity diode lasers

We present a compact,low-noise,and inexpensive optical phase-lock loop(OPLL) system to synchronize the frequency and the phase between two external cavity diode lasers. Based on a direct digital synthesizer technique,a programmable radio-frequency generator is implemented as the reference signal source. The OPLL has a narrow beat note linewidth below 1 Hz and a residual mean-square phase error of 0.06 rad~2 in a 10 MHz integration bandwidth. The experimental test results prove the competent performance of the system,which is promising as a low-budget choice in atomic physics applications.     

Blue diode pumped solid-state lasers for digital projection

Lasers present many advantages over currently used light sources for projection applications. Compact as well as efficient displays can be realized with RGB laser systems. The extreme brightness and collimation of lasers enable very efficient light collection. For portable, battery-powered microprojectors or even integrated devices, where the efficiency becomes even more critical, 50 mW per color is enough for a luminous flux on the projection screen of 20 lm. While blue and red diode lasers in this power range are becoming widely available, the bottleneck for this application is still the lack of integrated green laser sources. We present here a blue-diode pumped Pr³⁺-doped LiYF laser emitting at 523 nm. By optimizing on many aspects of the crystal and resonator, we increased the laser output power up to 169.4 mW, which corresponds to a total power conversion efficiency of 7%. Moreover, lasing in red can be obtained with the same crystal with similar or even better output powers. This makes the Pr:YLF laser an ideal candidate for an RGB projection source together with blue InGaN diodes.     

Picosecond optoelectronic characterization of diode lasers

New optoelectronic techniques for measuring semiconductor laser turn-on delay times and jitter with a picosecond temporal resolution are proposed and were employed for both conventional, homogeneous cavity and ion-bombarded picosecond diode laser characterization. Distinct differences in the characteristics of those lasers were found.