T. Tanbun-Ek

Subpicosecond monolithic colliding‐pulse mode‐locked multiple quantum well lasers

Ultrafast subpicosecond optical pulse generation is achieved by passive colliding‐pulse mode locking of monolithic multiple quantum well InGaAsP semiconductor lasers. Transform‐limited optical pulses with durations of 1.1, 0.83, 1.0, and 0.64 ps are achieved at repetition rates of 40, 80, 160, and 350 GHz, respectively, without using any external ac sources.

1.6W high wall plug efficiency, continuous-wave room temperature quantum cascade laser emitting at 4.6μm

A strain-balanced, InP-based quantum cascade laser structure designed for light emission at 4.6μm was grown by metal-organic chemical vapor deposition. A maximum total optical power of 1.6W was obtained in continuous-wave mode at 300K for uncoated devices processed in buried heterostructure geometry with stripe dimensions of 5mm by 9.5μm. Corresponding maximum wall plug efficiency and threshold current density were measured to be 8.8% and 1.05kA∕cm2, respectively. Fully hermetically packaged laser of identical dimensions produced in excess of 1.5W under the same conditions.

A systems perspective on digital interconnection technology

The work describes, from a switching system designers perspective, present digital interconnection technologies and needs. The discussion begins at the chip-to-chip interconnection level and proceeds to the frame-to-frame level. The authors evaluate the optimal packaging and interconnection technology that should be used in future system designs. The analysis suggests that parallel optical data links based on a laser array technology implemented at the board-to-board level are presently advantageous. This analysis, as well as a detailed description of laser gate arrays, is also included. >

Mode-locked hybrid soliton pulse source with extremely wide operating 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 mu m 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.<<ETX>>

Transform‐limited 1.4 ps optical pulses from a monolithic colliding‐pulse mode‐locked quantum well laser

We report the generation of short optical pulses from novel monolithic colliding‐pulse mode‐locked quantum well lasers. Transform‐limited pulses with durations of 1.4 ps at a repetition rate of 32.6 GHz have been achieved, with nearly 100% intensity modulation depth and a peak optical power of 10 mW. This is the shortest transform‐limited pulse directly generated from monolithic mode‐locked lasers (time‐bandwidth product =0.3).

Frequency response subtraction for simple measurement of intrinsic laser dynamic properties

The authors describe a new technique for extracting the intrinsic laser-diode dynamic properties accurately. This simple technique eliminates the need for accurate microwave calibration of the test equipment and problems of microwave reflections, nonideal frequency response of laser mount, and detector. The effect of the parasitic components of the laser diode are also eliminated from the results so that measurements of important dynamic properties of the laser can be found up to high frequencies (10-20 GHz) on standard laser diodes. The techinque being used to measure variations of resonance peak and damping factor at different bias levels for a standard bulk active region 1.3 mu m laser diode is shown.<<ETX>>

InGaAs/InP quantum well lasers with sub‐mA threshold current

We evaluate the effect of high‐reflectivity facet coatings on the threshold current of lattice matched and compressively strained InGaAs/InP quantum well lasers. A large decrease in the threshold current is observed in structures with low internal losses. Coated lasers exhibit threshold currents as low as 1.1 mA at 20 °C and 0.9 mA at 10 °C, down from ∼15 mA in as‐cleaved devices with cavity length of 200 μm. These changes are carefully modeled and the prospects for further reduction of the threshold current discussed.

Room-temperature continuous-wave quantum cascade lasers grown by MOCVD without lateral regrowth

We report on room-temperature continuous-wave (CW) operation of lambda~8.2 mum quantum cascade lasers grown by metal-organic chemical vapor deposition without lateral regrowth. The lasers have been processed as double-channel ridge waveguides with thick electroplated gold. CW output power of 5.3 mW is measured at 300 K with a threshold current density of 2.63 kA/cm2. The measured gain at room temperature is close to the theoretical design, which enables the lasers to overcome the relatively high waveguide loss

Stable single mode hybrid laser with high power and narrow linewidth

We describe hybrid lasers combining a semiconductor gain section and fiber cavity with integrated chirped Bragg reflector. These devices have produced output powers of 27.5 mW in a narrow linewidth (400 KHz) stable single longitudinal mode. The use of a chirped reflector to stabilize the single mode output, and correct grating orientation are described. The laser output has a side‐mode suppression ratio of over 55 dB at 27.5 mW output, and relative intensity noise (RIN) below 160 dB/Hz.

Analysis of gain in determining T/sub 0/ in 1.3 /spl mu/m semiconductor lasers

Rapid decrease of differential gain has been determined to dominate the temperature dependence of threshold current in 1.3-/spl mu/m multiquantum well and bulk active lasers giving rise to low values of T/sub 0/. Extensive experimental characterization of each type of device is described. Results are presented for the dependence of gain on chemical potential and carrier density as a function of temperature. The data indicate the important role of the temperature-insensitive, carrier density dependent chemical potential in determining differential gain. Modeling of the temperature dependence of threshold carrier density in MQW and bulk active lasers based on a detailed band theory calculation is described. The calculated value of T/sub 0/ depends on the structure of the active layer, e.g., multiquantum well versus bulk. However, the calculated values are substantially higher than measured. >