Characterization and modeling of gain spectra of single-layer InAs/InP(100) quantum dot amplifiers

In this contribution we present the small signal net modal gain measurement results of single-layer InAs/InP(100) quantum dot amplifiers in 1.6 to 1.8 µm wavelength range. The material shows sufficient optical gain to be used in the long-wavelength optical coherence tomography. The modal gain has been observed as a function of current density and temperature. An improved rate equation model has been applied to analyse the measurements. A good fit of the theory to the measurements was obtained with a temperature dependent carrier injection efficiency which is below 2%

Influence of an ultrathin GaAs interlayer on the structural properties of InAs/InGaAsP/InP (100) quantum dots investigated by cross-sectional scanning tunneling microscopy

Cross-sectional scanning tunneling microscopy is used to study at the atomic scale how the structural properties of InAsInGaAsPInP quantum dots _QDs_ are modified when an ultrathin _0–1.5 ML_ GaAs interlayer is inserted underneath the QDs. Deposition of the GaAs interlayer suppresses the influence of the AsP exchange reaction on QD formation and leads to a planarized QD growth surface. A shape transition from quantum dashes, which are strongly dissolved during capping, to well defined QDs takes place when increasing the GaAs interlayer thickness between 0 and 1.0 ML. Moreover, the GaAs interlayer allows the control of the AsP exchange reaction, reducing the QD height for increased GaAs thicknesses above 1.0 ML, and decreases the QD composition intermixing, producing almost pure InAs QDs

Measurement and analysis of temperature-dependent optical modal gain in single-layer InAs/InP(100) quantum-dot amplifiers in the 1.6- to 1.8-µm wavelength range

In this paper, measurements and analysis of the small-signal net modal gain of single-layer InAs/InP(100) quantum-dot (QD) optical amplifiers are presented. The amplifiers use only a single layer of InAs QDs on top of a thin InAs quantum well. The devices have been fabricated using a layer stack that is compatible with active–passive integration scheme, which makes further integration possible. The measurement results show sufficient optical gain in the amplifiers and can thus be used in applications such as lasers for long-wavelength optical coherence tomography and gas detection. The temperature dependence of the modal gain is also characterized. An existing rate-equation model was adapted and has been applied to analyze the measured gain spectra. The current injection efficiency has been introduced in the model to obtain a good fit with the measurement. It is found that only a small portion ($sim$1.7%) of the injected carriers is actually captured by the QDs. The temperature dependence of several parameters describing the QDs is also discovered. The mechanisms causing the blue shift of peak gain as the current density increases and the temperature changes are analyzed and discussed in detail

Temperature-Compensated Solution Concentration Measurements Using Photonic Crystal Fiber-Tip Sensors

We demonstrate fiber optic sensors with temperature compensation for the accurate measurement of ethanol concentration in aqueous solutions. The device consists of two photonic crystal (PhC) fiber-tip sensors: one measures the ethanol concentration via refractive index (RI) changes and the other one is isolated from the liquid for the independent measurement of temperature. The probes utilize an optimized PhC design providing a Lorentzian-like, polarization-independent response, enabling a very low imprecision (pm-level) in the wavelength determination. By combining the information from the two probes, it is possible to compensate for the effect that the temperature has on the concentration measurement, obtaining more accurate estimations of the ethanol concentration in a broad range of temperatures. We demonstrate the simultaneous and single-point measurements of temperature and ethanol concentration in water, with sensitivities of 19 pm/°C and ∼53 pm/%, in the ranges of 25 °C to 55 °C and 0 to (Formula presented.) (at 25 °C), respectively. Moreover, a maximum error of (Formula presented.) in the concentration measurement, with a standard deviation of ≤0.8%, was obtained in the entire temperature range after compensating for the effect of temperature. A limit of detection as low as (Formula presented.) was demonstrated for the concentration measurement in temperature-stable conditions.</p

Wavelength tuning of InAs/InP quantum dots: Control of As/P surface exchange reaction

Wavelength tuning of single and vertically stacked InAs quantum dot [QD] layers embedded inInGaAsP/InP [100] grown by metal organic vapor-phase epitaxy is achieved by controlling theAs/P surface exchange reaction during InAs deposition. The As/P exchange reaction is suppressedfor decreased QD growth temperature and group V-III flow ratio, reducing the QD size andphotoluminescence [PL]emission wavelength. The As/P exchange reaction and QD PL wavelengthare then reproducibly controlled by the thickness of an ultrathin [0¿2 ML] GaAs interlayerunderneath the QDs. Submonolayer GaAs coverages result in a shape transition from QDs toquantum dashes at low group V-III flow ratio. Temperature dependent PL measurements revealexcellent optical properties of the QDs up to room temperature with PL peak wavelengths in thetechnologically important 1.55 ¿region for telecom applications. Widely stacked QD layers arereproduced with identical PL emission to increase the active volume, while closely stacked QDlayers reveal a systematic PL redshift and linewidth reduction due to vertical electronic couplingwhich is proven by the linear polarization of the cleaved-side PL changing from in plane toisotropic. ¿ 2006 American Vacuum Society

First demonstration of single-layer InAs/InP (100) quantum-dot laser : continuous wave, room temperature, ground state

Reported is the first InAs/InP (100) quantum-dot (QD) laser operating in continuous-wave mode at room temperature on the QD ground state transition employing a single-layer of QDs grown by metal organic vapour phase epitaxy. The necessary high QD density is achieved by growing the QDs on a thin InAs quantum well (QW). These QDs on the QW laser exhibit a high slope efficiency and a lasing wavelength of 1.74 µm, which is important for biomedical applications