Room-temperature operation of InAs quantum-dash lasers on InP (001)

The first self-assembled InAs quantum dash lasers grown by molecular beam epitaxy on InP (001) substrates are reported. Pulsed room-temperature operation demonstrates wavelengths from 1.60 to 1.66 μm for one-, three-, and five-stack designs, a threshold current density as low as 410 A/cm² for single-stack uncoated lasers, and a distinctly quantum-wire-like dependence of the threshold current on the laser cavity orientation. The maximal modal gains for lasing in the ground-state with the cavity perpendicular to the dash direction are determined to be 15 cm^-1 for single-stack and 22 cm^-1 for five-stack lasers     

High-power AlGaInAs strained multiquantum well lasers operating at 1.52 /spl mu/m

1.75 W CW power in AlGaInAs-InP strained QW lasers is demonstrated. Room temperature threshold current densities are 410 A/cm/sup 2/, and the characteristic temperature is 69 K. The variation in the external differential efficiency with cavity length and temperature reveal the optimum length and show how nonradiative recombination mechanisms limit the performance.     

The influence of quantum-well composition on the performance ofquantum dot lasers using InAs-InGaAs dots-in-a-well (DWELL) structures

The optical performance of quantum dot lasers with different dots-in-a-well (DWELL) structures is studied as a function of the well number and the indium composition in the InGaAs quantum well (QW) surrounding the dots. While keeping the InAs quantum dot density nearly constant, the internal quantum efficiency η_i, modal gain, and characteristic temperature of 1-DWELL and 3-DWELL lasers with QW indium compositions from 10 to 20% are analyzed. Comparisons between the DWELL lasers and a conventional In_0.15Ga_0.85As strained QW laser are also made. A threshold current density as low as 16 A/cm² is achieved in a 1-DWELL laser, whereas the QW device has a threshold 7.5 times larger. It is found that η_i and the modal gain of the DWELL structure are significantly influenced by the quantum-well depth and the number of DWELL layers. The characteristic temperature T₀ and the maximum modal gain of the ground-state of the DWELL structure are found to improve with increasing indium in the QW It is inferred from the results that the QW around the dots is necessary to improve the DWELL laser's η_i for the dot densities studied     

Optical gain and absorption of quantum dots measured using an alternative segmented contact method

An alternative segmented-contact method for accurate measurement of the optical gain and absorption of quantum-dot and quantum-dash active materials with small optical gain is reported. The usual error from unguided spontaneous emission is reduced by subtracting signals acquired from three independently controlled sections as opposed to just two found in the conventional technique. The quantum-dot gain spectra are measured to a precision of less than 0.2 cm/sup -1/ at nominal gain values below 2 cm/sup -1/, and gain spectrum of quantum-dash sample is calculated with an error less than 0.3 cm/sup -1/ at a gain less than 1 cm/sup -1/. These accuracies are checked with a self-calibrating method. The internal optical mode loss measurement is also described.     

150-nm tuning range in a grating-coupled external cavityquantum-dot laser

An antireflection (AR) coated single-stack quantum-dot (QD) laser in a grating-coupled external cavity is shown to operate across a tuning range from 1.095 μm to 1.245 μm. This 150-nm range extends from the energy levels of the ground state to excited states. At any wavelength, the threshold current density is no greater than 1.1 kA/cm ². This large tunable range is the product of the rapid carrier filling of the higher energy states under a low pumping current and homogeneous broadening in the QD ensemble. The possibility of a larger tuning range is discussed with the further improvement of the AR-coating     

Low-threshold quantum dot lasers with 201 nm tuning range

A grating-coupled external-cavity quantum dot laser is tuned across a 201 nm range at a maximum bias of 2.87 kA/cm². One order of magnitude less than the bias required for comparable tuning of quantum well lasers. The tuning range increases for higher cavity losses of the quantum dot laser