G.E. Shtengel

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. >

Role of p-doping profile and regrowth on the static characteristics of 1.3-/spl mu/m MQW InGaAsP-InP lasers: experiment and modeling

In this paper, we study both experimentally and theoretically how the change of the p-doping profile, particularly the p-i junction placement, affects the output characteristics of 1.3-/spl mu/m InGaAsP-InP multiple-quantum-well (MQW) lasers. The relationship between the p-doping profile before and after regrowth is established, and the subsequent impact of changes in the p-i junction placement on the device output characteristics, is demonstrated. Device characteristics are simulated including carrier transport, capture of carriers into the quantum wells, the quantum mechanical calculation of the properties of the wells, and the solution for the optical mode and its population self-consistently as a function of diode bias. The simulations predict and the experiments confirm that an optimum p-i junction placement simultaneously maximizes external efficiency and minimizes threshold current. Tuning of the base epitaxial growth Zn profile allows one to fabricate MQW devices with a threshold current of approximately 80 A/cm/sup 2/ per well for devices with nine QWs at room temperature or lasers with a characteristic temperature T/sub 0/=70 K within the temperature range of 20/spl deg/C-80/spl deg/C.

Impedance‐corrected carrier lifetime measurements in semiconductor lasers

Differential carrier lifetime as a function of subthreshold bias current in 1.3 m bulk active lasers is obtained by measurement of small‐signal modulation of amplified spontaneous emission together with careful characterization of frequency‐ and current‐dependent device impedance. The strong influence of rapidly varying device impedance upon these measurements is illustrated. In contrast to other studies, neither saturation of differential lifetime at low currents nor linear dependence of spontaneous emission on carrier density is observed. Recombination parameters, fit from current versus carrier density, along with consistent fits of spontaneous emission versus carrier density, are presented.

Analysis of T0 in 1.3 μm multi‐quantum‐well and bulk active lasers

Temperature dependence of threshold in 1.3 μm semiconductor lasers is analyzed in terms of contributions due to gain, internal efficiency, internal loss, and nonradiative recombination. Rapid decrease of differential gain and roughly proportional increase in transparency carrier density are determined to dominate temperature dependence of threshold current. Auger recombination is found to play a secondary role in reducing T0 by compounding the effects of rapidly increasing threshold carrier density.

Temperature performance of 1.3-μm InGaAsP-InP lasers with different profile of p-doping

Temperature dependencies of the threshold current, device slope efficiency, and heterobarrier electron leakage current from the active region of InGaAsP-InP multiquantum-well (MQW) lasers with different profiles of acceptor doping were measured. We demonstrate that the temperature sensitivity of the device characteristics depends on the profile of p-doping, and that the variance in the temperature behavior of the threshold current and slope efficiency for lasers with different doping profiles cannot be explained by the change of the measured value of the leakage current with doping only. The entire experimental data can be qualitatively explained by suggesting that doping ran affect the value of electrostatic band profile deformation that affects temperature sensitivity of the output device characteristics. We show that doping of the p-cladding/SCH layer interface in InGaAsP-InP MQW lasers leads to improvement of the device temperature performance.

Gain characteristics of 1.55-μm high-speed multiple-quantum-well lasers

We describe the important characteristics of high-speed p-doped compressively strained MQW lasers obtained from comprehensive below-threshold DC measurements. Results of gain and differential gain versus wavelength and carrier density are verified by above-threshold resonance measurements. Measurement-derived design curves of gain, differential gain, and linewidth enhancement factor allow device optimization for high speed and low chirp.<<ETX>>

Wavelength chirp and dependence of carrier temperature on current in MQW InGaAsP-InP lasers

In this paper, we derive a relation between the wavelength chirp and carrier temperature in semiconductor lasers. The coefficient relating the change in carrier temperature and chirp is expressed in terms of the temperature derivative of the optical gain, and two parameters describing the variation of refractive index produced by the variation of optical gain due to change of carrier quasi-Fermi level separation or carrier temperature. We have measured these parameters for MQW InGaAsP lasers, Using this data, we estimated the rate of the temperature increase with current above threshold in these devices, which is 0.13 K/mA.

Statistical correlation between first and second-order PMD

We investigate the statistical correlation between first- and second-order polarization mode dispersion (PMD) effects, which is important for PMD mitigation. The theoretical results are compared to numerical simulations and experimental data from a real high-PMD fiber. A new dependence between first- and second-order PMD is found. We show that the root mean square (RMS) value of the second-order PMD component, perpendicular to the PMD vector, increases with the length of the PMD vector.

Statistical dependence between first and second-order PMD

We measure the first and the second-order polarisation mode dispersion (PMD) in high-PMD fiber, and determine correlation between the first and second-order PMD. Theory and measurements are in a good agreement. We follow a definition of two second-order components of second order PMD: component parallel to PMD vector, called polarization dependent chromatic dispersion (PCD), and perpendicular to the PMD vector component, causing depolarization. We investigate the statistics of both components of second order PMD vector as functions of differential group delay.

High-speed, low chirp, directly modulated 1.55-/spl mu/m DFB laser sources for 10 Gbit/s local distribution

Summary form only given. In this paper we describe 1.55-/spl mu/m DFB lasers for communications applications using p-doped compressively strained multiple quantum well (MQW) active regions to provide devices with extremely high modulation bandwidths and low wavelength chirp.