Marcus Duelk

Thermal resistance reduction in high power superluminescent diodes by using active multi-mode interferometer

Low thermal resistance of high power superluminescent diodes (SLEDs) by using active multi-mode interferometer (active-MMI) is presented in this paper. The active layer temperature evaluation demonstrates that the power saturation mechanism in active-MMI SLED is heat for the first time. Low thermal resistance of 4.83u2009K/W in active-MMI SLEDs leads to a high power of 115u2009mW. Moreover, the effect of the active area size on the output power is demonstrated both experimentally and theoretically. Good agreement between the theoretical and experimental results indicates that active-MMI configuration is a new design in support of efficient heat dissipation and thermal resistance reduction for SLEDs.

High-Power (

We have designed and fabricated, for the first time to our knowledge, novel superluminescent diodes by using active multimode interferometers that emit at a wavelength of 1.55 ¿ m. An output power as high as 115 mW was obtained with a wide 3-dB bandwidth of 50 nm and low spectral ripple of 0.03 dB. In addition, they showed stable single-transverse-mode outputs up to the maximum output power.

> 110

We report on the achievement of III-nitride blue superluminescent light-emitting diodes on GaN substrates. The epitaxial structure includes an active region made of In0.12Ga0.88N quantum wells in a GaN/AlGaN waveguide. Superluminescence under cw operation is observed at room temperature for a current of 130 mA and a current density of 8u2002kA/cm2. The central emission wavelength is 420 nm and the emission bandwidth is ∼5u2002nm in the superluminescence regime. A peak optical output power of 100 mW is obtained at 630 mA under pulsed operation and an average power of 10 mW is achieved at a duty cycle of 20%.

mW) Superluminescent Diodes by Using Active Multimode Interferometer

We report on the characteristics of blue superluminescent light emitting diodes based on the emission of InGaN quantum wells. Narrow ridge-waveguide devices realized by standard processing techniques and with extremely low facet reflectivity show single lateral mode emission and continuous-wave output powers >35 mW with a typical spectral bandwidth of 4–5 nm. Tuning the composition of the active region, superluminescent light emitting diodes spanning all the spectral range between 410 and 445 nm could be realized. The light output is highly directional and results in a coupling efficiency into single mode fibers >50%. The device temperature behavior is also discussed.

Broadband blue superluminescent light-emitting diodes based on GaN

We demonstrate state-of-the-art p-type (Al)GaN layers deposited at low temperature (740u2009°C) by ammonia molecular beam epitaxy (NH3-MBE) to be used as top cladding of laser diodes (LDs) with the aim of further reducing the thermal budget on the InGaN quantum well active region. Typical p-type GaN resistivities and contact resistances are 0.4u2009Ωu2009cm and 5u2009×u200910−4u2009Ωu2009cm2, respectively. As a test bed, we fabricated a hybrid laser structure emitting at 400u2009nm combining n-type AlGaN cladding and InGaN active region grown by metal-organic vapor phase epitaxy, with the p-doped waveguide and cladding layers grown by NH3-MBE. Single-mode ridge-waveguide LD exhibits a threshold voltage as low as 4.3u2009V for an 800u2009×u20092u2009μm2 ridge dimension and a threshold current density of ∼5u2009kAu2009cm−2 in continuous wave operation. The series resistance of the device is 6u2009Ω and the resistivity is 1.5u2009Ωu2009cm, confirming thereby the excellent electrical properties of p-type Al0.06Ga0.94N:Mg despite the low growth temperature.

High Power Blue-Violet Superluminescent Light Emitting Diodes with InGaN Quantum Wells

We report on the fabrication of InGaN-based multiple-quantum-well laser diodes (LDs) emitting at 420 nm. Structures with standard claddings (p- and n-AlGaN), asymmetric claddings (p-GaN and n-AlGaN), and AlGaN-free claddings were grown by metal organic vapor phase epitaxy on polar c-plane free-standing GaN substrates. Electrical and optical properties of each LD are presented. Thanks to an optimized design of the InGaN waveguide and active region, cw lasing of a completely AlGaN-free laser diode is demonstrated, with a threshold current density <5 kA/cm2 and a differential efficiency per facet of ~0.4 W/A without high-reflection coatings.

Low temperature p-type doping of (Al)GaN layers using ammonia molecular beam epitaxy for InGaN laser diodes

We report on InGaN edge emitting laser diodes with a top metal electrode located beside the laser ridge. Current spreading over the ridge is achieved via a highly doped n(+)-type GaN layer deposited on top of the structure. The low sheet resistance of the n(+)-GaN layer ensures excellent lateral current spreading, while carrier injection is confined all along the ridge thanks to current tunneling at the interface between the n(+)-GaN top layer and the p(++)-GaN layer. Continuous-wave lasing at 400nm with an output power of 100mW is demonstrated on uncoated facet devices with a threshold current density of 2.4 kA.cm(-2)

AlGaN-Free Blue III–Nitride Laser Diodes Grown on c-Plane GaN Substrates

We demonstrate hybrid laser diodes by combining n-type layers and an active region grown by metal organic vapor phase epitaxy with p-type layers grown by molecular beam epitaxy. These p-doped layers, grown at 740 degrees C, exhibit state-of-the-art electrical characteristics and prevent the indium-rich quantum wells from thermal degradation. Narrow ridge-waveguide lasers with high-reflectivity coatings show a threshold current density of 9.7 kA.cm(-2), a threshold voltage of 5.4V, and a lasing wavelength of 501 nm. The internal optical loss and material gain of the epitaxial structures are also measured and discussed

InGaN laser diode with metal-free laser ridge using n+-GaN contact layers

We report on the reliability of GaN-based super-luminescent light emitting diodes (SLEDs) emitting at a wavelength of 405 nm. We show that the Mg doping level in the p-type layers has an impact on both the device electro-optical characteristics and their reliability. Optimized doping levels allow decreasing the operating voltage on single-mode devices from more than 6 V to less than 5 V for an injection current of 100 mA. Furthermore, maximum output powers as high as 350 mW (for an injection current of 500 mA) have been achieved in continuous-wave operation (CW) at room temperature. Modules with standard and optimized p-type layers were finally tested in terms of lifetime, at a constant output power of 10 mW, in CW operation and at a case temperature of 25 °C. The modules with non-optimized p-type doping showed a fast and remarkable increase in the drive current during the first hundreds of hours together with an increase of the device series resistance. No degradation of the electrical characteristics was observed over 2000 h on devices with optimized p-type layers. The estimated lifetime for those devices was longer than 5000 h.