Milliwatt second harmonic generation in quantum cascade lasers with modal phase matching

Milliwatt second harmonic power at 4.45 /spl mu/m was achieved in InP lattice-matched quantum cascade lasers with monolithically-integrated resonant nonlinear cascades and modal phase matching. The use of an InP top-cladding layer and high-reflectance coating on the laser back facet enabled high linear laser power and consequently record nonlinear power.     

A new InGaAs/InGaAsP delta -strained multiple-quantum-well laser grown by chemical-beam epitaxy

The authors propose and demonstrate a delta -strained multiple-quantum-well laser in which the quantum well is composed of a thin strained layer ( approximately AA In/sub x/Ga/sub 1-x/As) sandwiched by lattice-matched (In/sub 0.53/Ga/sub 0.47/As) layers. A threshold current density of 510 A/cm/sup 2 /was obtained from broad-area lasers with four delta -strained quantum wells and a cavity length of 3 mm, with an emission wavelength near 1.55 mu m. The use of a delta -strained quantum well provides an additional degree of freedom in optimizing the amount of strain and thickness of the active layer in improving the device performance.<>     

Superfast 1.55 mu m DFB lasers

Singlemode 1.55 mu m distributed feedback lasers with a modulation bandwidth of 22.5 GHz are reported. The devices use p-doped, strained multiquantum-well active regions to reduce the bandwidth limitations caused by hole transport, as well as increasing the intrinsic response of the device. The present 22.5 GHz bandwidth is limited by device parasitics.<>     

Long-wavelength InGaAsP/InP distributed feedback lasersincorporating gain-coupled mechanism

Successful operation of long-wavelength InGaAsP low-threshold-current gain-coupled DFB lasers was demonstrated by using an InGaAsP quaternary grating that absorbs the DFB (distributed feedback) emission. The amount of gain (loss)-coupling is controlled by the composition (bandgap) and thickness of the grating quaternary and the InP-spacer layer between the grating and the active layer. With optimally designed lasers, CW (continuous-wave) threshold currents were 10-15 mA (250-μm cavity, as-cleaved), slope efficiency was ~0.4 mW/mA (both facets) and SMSR (side-mode suppression ratio) was as high as 52 dB. The laser operated in the same DFB mode with SMSR staying ~50 dB throughout the entire current range. At 100°C, the CW threshold current stayed low, ~50 mA, and SMSR was ~40 dB. Results also indicate that the presence of gain-coupling removes the degeneracy in lasing wavelength     

Mode-locked hybrid soliton pulse source with extremely wideoperating frequency range

The authors report a mode-locked pulse source with extremely wide operating frequency range and very stable operation, through the use of a long, linearly chirped Bragg reflector as the output coupler integrated in a fiber external cavity. A 1.55 μm strained MQW laser diode is used, with one facet high reflectivity (HR) coated for improved cavity Q, and the other antireflection (AR) coated to allow coupling to the external cavity and suppress Fabry-Perot modes. Near-transform-limited pulses are obtained over a frequency range of 700 MHz around a system operating frequency of 2.488 GHz, with pulsewidths of 50 ps, as required for a practical soliton transmission system     

DFB lasers with monolithically integrated passive waveguide

Novel MQW integrated passive waveguide (IPW) DFB lasers have been fabricated using a selective area MOVPE growth technique. Detailed measurements of the absorption loss of the passive waveguide in the structure as well as its influences on the laser linewidth are reported for the first time. A linewidth reduction factor of more than 3 is observed as compared to a simple DFB laser despite the high absorption loss     

Spectral bandwidth broadening for long-haul submarine WDMapplications using phosphorus-aluminium-codoped EDFAs

The authors demonstrate that single stage phosphorus-aluminium-codoped EDFAs greatly increase the usable spectral bandwidth for long-haul submarine applications. With such an amplifier, a total gain excursion of 5 dB was measured for eight WDM channels spanning 11 nm, with a total power budget of 1150 dB     

Intercalation of Toluidines into α-Zirconium Hydrogenphosphate

Intercalates of o-, m-, and p-toluidine into α-Zr(HPO₄)₂ · H₂O were prepared and characterized by powder X-ray diffraction, thermogravimetric analysis and infrared spectroscopy. As follows from IR, toludine molecules are protonated in the interlayer space. Toluidine molecules are arranged in a bimolecular way in the intercalates containing more than 1.5 toluidine molecules per Zr atom. On the other hand, a monolayer of the toluidine molecules is supposed in the intercalates with less than one toluidine molecule per Zr atom.