Surface-emitting Laser Diode Arrays Research Articles

Supermode Analysis and Characterization of Triangular Vertical Cavity Surface Emitting Laser Diode Arrays

Supermode Analysis and Characterization of Triangular Vertical Cavity Surface Emitting Laser Diode Arrays

Modal characteristics of coupled vertical cavity surface emitting laser diode arrays

The modal characteristics of dual-element coupled vertical cavity surface emitting laser (VCSEL) arrays are analyzed numerically and experimentally. A photonic crystal pattern etched into the top mirror optically defines the two elements of the array that are independently electrically biased. Using a two-dimensional complex waveguide analysis, we incorporate the effects of varying temperature and electron plasma-induced index suppression arising from asymmetric injection. The simulations are compared to experimental characterization of output power, lasing spectra, and far-field beam profile as a function of the two independent injection currents. Three distinct operating regimes are identified for the arrays: single independent local mode; a region of two modes that are primarily localized into a specific cavity; and a region of two supermodes whose fields extend across both elements. This analysis provides a physical intuition for the behavior of the dual-element coupled VCSEL array across its full operating range for emerging applications.

Supermode Switching in Coherently-Coupled Vertical Cavity Surface Emitting Laser Diode Arrays

We report and analyze the supermode switching with current injection found for coherently-coupled dual-element vertical cavity surface emitting laser arrays. The output power, spectral characteristics, and far-field mode profile are measured for a range of bias current operating conditions. The coupling-induced enhanced output power from an in-phase or out-of-phase supermode is confirmed when approximately equal currents are injected into each array element. We observe that the coherent supermode switches from out-of-phase to in-phase supermode with increasing equal current injection. The switching is found to be consistent with coupled mode theory and a 1-dimensional spatial supermode model. The calculated modal gain of the out-of-phase and in-phase array supermodes are consistent with the observed switching of the coherent supermodes.

Non-Hermiticity and exceptional points in coherently coupled vertical cavity laser diode arrays

Coherently coupled laser arrays can be described by the temporal coupled mode theory in which the array modal behavior can be classified according to the coupling matrix, M¯¯. Accounting for a nonuniform gain/loss distribution in a laser array makes M¯¯ a non-Hermitian matrix, and experimentally we find phase-front tuning (beam steering) of the coherent supermode as a result of the non-Hermiticity. We report the experimental characterization of the supermodes in coherently coupled vertical cavity surface emitting laser diode arrays and demonstrate control of non-Hermiticity by spatially varying injection currents. Exceptional points are identified in these electrically injected microcavity diode arrays.

高速レーザープリンタ用VCSELアレイ

高速レーザープリンタ用VCSELアレイ

Multiple-beam time-of-flight sensor based on a vertical cavity surface emittinglaser diode array

A novel and low-cost time-of-flight sensor with multiple laser beams focused in themeasurement volume is described. The time-of-flight sensor is based on avertical cavity surface emitting laser diode array and a clean-imaging(4f)system, projecting the near field of the emitted light into the measurementvolume. The imaging system is tested both with and without an optionalcylindrical lens, producing either multiple light sheets or spots in themeasurement volume, respectively. Work is carried out to characterize the lightdistribution in the measurement volume, and to apply the sensor to liquid flowmeasurements. The sensor measures velocity with a low signal-to-noise ratio, lowtemperature influence on the calibration factor and the ability to determine thedirection of the velocity.

2.5 Gbit∕s∕channel laser driver design for four-channel parallel optic transceiver using SiGe BiCMOS technology

A laser driver for a four-channel parallel fibre optic transceiver operating up to 2.5 Gbit/s is designed using a 0.35 /spl mu/m SiGe BiCMOS process. An 850 nm vertical cavity surface emitting laser diode array is used as a light source. The measurement was performed under the case temperature range 0-80/spl deg/C at 3.1 to 3.5 V power supply variations. Using a gigabit Ethernet filter, a 45% eye mask margin has been achieved at -4 dBm average optical power and 7 dB extinction ratio at 40/spl deg/C. The rise/fall time is less than 100 ps. The measured deterministic jitter is under 60 ps and the random jitter under 4 ps RMS.

Laser action from a 2,6,8-position trisubstituted 1,3,5,7-tetramethylpyrromethene-BF_2 complex: part 3

Some laser action properties of a new Pyrromethene-BF(2) complex, 1, 3, 5, 7-tetramethyl-8-ethyl-2, 6-dicyanopyrromethene-BF(2) complex are reported. This laser dye exhibits laser action in the green-yellow portion of the spectrum, and its laser action efficiency was ~350% higher compared with Coumarin 545. Exceptional photostability of the new laser dye was observed when a mixture of 1, 4-dioxane:heptane ratio of 1:4 was used as the solvent. Further, it is suggested that dye lasers can be upscaled to high average power output when surface-emitting laser diode arrays are used as pump (excitation) sources.

Five-wavelength surface emitting laser diode array based on postgrowth adjustment of emission wavelength

A five-wavelength surface emitting laser diode array based on surface mode emission is reported. The wavelength control is achieved by postgrowth adjustment of the surface structure. Wavelength spacing between laser groups is 1.1 nm in average and the wavelength reproducibility is ±0.13 nm. The total change in the emission wavelength over the array is 4.78 nm. The single array elements show single mode emission with a full width at half-maximum of 0.08 nm in average and a side mode suppression ratio up to 20 dB. This type of laser diode is of high interest for wavelength division multiplexing applications.

High speed performance of 2-D vertical-cavity laser diode arrays

We have fabricated and tested 10×10 independently addressable vertical-cavity surface-emitting laser diode arrays. Arrays with 55 μm active diameter devices show an average threshold current density of 590 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and an excellent homogeneity of the output characteristics over the full array size with maximum CW output powers of 12 mW. Broad area laser diodes with active diameters of 75 μm reach output powers of 18 mW for CW operation and 180 mW under pulsed conditions. Small-signal modulation bandwidths are beyond 10 and 8 GHz for the 55 and 75 μm devices, respectively.

8/spl times/8 independently addressable vertical-cavity surface-emitting laser diode arrays grown by MOCVD

The first 8/spl times/8 independently addressable vertical-cavity surface-emitting laser diode arrays have been grown by MOCVD. They showed not only good I-L characteristics, such as low threshold current and voltage, but excellent uniformity of threshold current (3.39/spl plusmn/O.11 mA) and lasing wavelength (850.93/spl plusmn/0.28 nm). These results shows that the high-productivity of MOCVD growth technique is applicable to the fabrication of such laser diode arrays. >

Lateral mode control of grating surface emitting laser diode arrays by monolithic Talbot filtering

Talbot filters can provide passive lateral mode control in monolithic two-dimensional phased arrays of grating surface emitting lasers. This was shown with computer modeling by numerical integration of the interference of Huygens wavelets and by experiment. The modeling also indicates sufficient robustness of the Talbot filtering technique for typical fabrication tolerances. Experimental measurements demonstrated that lateral mode control could be selected for either the in-phase or the antiphase mode, depending on the placement of the Talbot filters.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Linewidth, tunability, and VHF-millimeter wave frequency synthesis of vertical-cavity GaAs quantum-well surface-emitting laser diode arrays

The authors report the measurement of the laser linewidth, wavelength tunability, and generation of microwave frequencies between individually addressable elements of a vertical-cavity GaAs quantum-well surface-emitting laser diode array (lasing in the wavelength range 850-865 nm). Using heterodyne techniques, the authors obtain a deconvolved 65 MHz laser linewidth from the 109 MHz beat signal. The laser linewidth corresponds to a semiconductor laser linewidth enhancement factor alpha =5.7, which is in excellent agreement with that obtained independently from optical gain measurements and corresponding calculated refractive index changes. The authors measured heterodyne beat frequencies of 2-20 GHz. The bandwidth was limited by the microwave amplifiers. A simple calculation shows that a tuning range of 65 MHz to 3 THz can be achieved. >

Heterodyne measurement of linewidth, tunability, and frequency synthesis of vertical-cavity surface-emitting laser diode arrays

The linewidth of vertical-cavity surface-emitting lasers (VCSELs) (65 MHz), the tunability of their lasing wavelength (20 AA), and the tunability of the heterodyne beat frequency (65 MHz to 150 GHz) were measured by varying the drive current to the lasers. The ability to control the output wavelength of VCSELs by current and location on the wafer makes it possible to extrapolate tunability over a range from 65 MHz to 3 THz. While the spatial tunability of 3 THz is of interest for wavelength-division multiplexing schemes, the current tunability of 150 GHz is attractive for frequency control and stabilization. The observation of narrow VCSEL linewidths is encouraging for their potential applications in communications.