InGaAsP Quantum Wells Research Articles

InGaAsP VECSEL for watt-level output at a wavelength around 765 nm.

We demonstrate a deep-red-emitting vertical external-cavity surface-emitting laser (VECSEL) with an emission wavelength around λ = 765 nm based on InGaAsP/GaInP quantum wells. The quaternary material system was characterized with x-ray diffraction of thin films as the basis for InGaAsP quantum wells, which are incorporated into an 11 × 1 quantum well active region. The surface morphology of the fabricated VECSEL structure is analyzed with atomic force microscopy and the laser is evaluated in a linear cavity for various heatsink temperatures resulting in a watt-level output power of Pmax,-15°C = 1.71 W in a fundamental transverse mode.

A Widely Tunable Three-Section DBR Lasers for Multi-Species Gas Detection

We demonstrate a widely tunable distributed Bragg reflector (DBR) laser operating at 1.8-µm, in which the DBR section was butt-jointed InGaAsP (λ = 1.45 μm) material. Through current and temperature tuning, a widely tuning range of over 11 nm with a side mode suppression ratio (SMSR) higher than 30 dB is obtained. Utilizing this DBR laser, the water and methane detection experiment has been successfully implemented, which illustrates the potential capacity of such DBR laser as the light source used for multispecies gas sensing. The work also illustrates that the butt-joint active-passive integration technology developed for the InGaAsP quantum-wells (QWs) can be successfully applied in the InGaAs QWs.

A Comparative Study on Optical Characteristics of InGaAsP QW Heterostructures of Type-I and Type-II Band Alignments

In this paper, we have configured InGaAsP QW (quantum well) heterostructures of type-I and type-II band alignments and simulated their optical characteristics by solving 6 x 6 Kohn-Luttinger Hamiltonian Matrix. According to the simulation results, the InGaAsP QW heterostructure of type-I band alignment has been found to show peak optical gain (TE mode) of the order of~3600/cm at the transition wavelength~1.40 µm; while of type-II band alignment has achieved the peak gain (TE mode) of the order of~7800/cm at the wavelength of~1.85 µm (eye safe region). Thus, both of the heterostructures can be utilized in designing of opto-or photonic devices for the emission of radiations in NIR (near infrared region) but form the high gain point of view, the InGaAsP of type-II band alignment can be more preferred.

Selective release of InP heterostructures from InP substrates

The authors report here a method of protecting the sidewall for the selective release of InGaAsP quantum-well (QW) heterostructure from InP substrates. An intact sidewall secured by SiO2 was demonstrated during the sacrificial layer selective etching, resulting in the suspended InGaAsP QW membranes which were later transferred to the Si substrate with polydimethylsiloxane stamp. The quality of the transferred InGaAsP QW membranes has been validated through photoluminescence and EL measurements. This approach could extend to arbitrary targeting substrate in numerous photonics and electronics applications.

The effects of external strain on the gain of InGaAsP quantum well

The effects of external strain on the gain of InGaAsP quantum well

Research on MeV pulsed radiation detection based on refractive index modulaiton

High time resolution detecting systems for MeV pulsed radiation are essential for inertial confinement fusion diagnostics. Traditional detection of system time resolution is restricted by cable bandwidth. Based on recording excess carrier dynamics in semiconductors, a new detecting mechanism, called RadOptic, was developed by Lawrence Livermore National Laboratory (LLNL). The variation of intensity of pulsed radiation with time was converted into the variation of intensity of infrared laser probe by using this mechanism. The sensing material was InGaAsP quantum wells with severalmicrometer thickness. Picosecond time resolution for several keV pulsed radiation has been demonstrated. The reported system is not suitable for MeV pulses due to its low efficiency to MeV photons. Multiple cascaded structure for MeV photon to electron transformation was proposed by LLNL. Applying bulk material with several-hundredmicrometer thickness is an alternative. Based on transient free carrier absorption, a system recording bulk materials' instantaneous refractive index change is established. The system consists of a probe laser, an interferometer module, a signal transmission module and a signal recording module. The probe is a tunable infrared continuous wave laser whose wavelength is ~1453 nm, guided by single mode fiber to the interferometer. The interferometer consists of a single mode fiber head coupled directly with the polished face of a bulk semiconductor. The interference pattern forms by multiple beams reflected from the front face and the back face of the bulk. Part of interference light is coupled to the single mode fiber and forms the output signal. Pulsed radiation will deposit energy and generate excess carriers in the bulk material. The refractive index of the bulk material changes therewith according to the Drude model. The interference pattern and the light coupled to the single mode fiber also change therewith. The signal is transmitted by a long single mode fiber. The signal recording module consists of photoelectric detectors and a digital oscilloscope. The signal generation process and the time resolution of the system are analyzed. Intrinsic GaAs refractive index change is exploited under electron pulses and X ray pulses. The analysis of signal generation process shows that when the excess carriers recombine much faster/much slower than the pulse width, the output signal/output signal differential can be viewed as a measure of intensity variation with time of the incident pulse. For this prototype system, the time resolution is restricted by the digital oscilloscope to 1 GHz. Bulk intrinsic GaAs demonstrates 30 ns refractive index response time, which is longer than the incident pulse width. The differential signal can be viewed as a measure of incident pulse intensity when GaAs is exposed to 1 ns~0.2 MeV electrons pulses. The differential signal width is shorter than the pulse width when GaAs is exposed to 5 ns~0.2 MeV electrons pulses. Auger recombination process may occur in the pulse duration under this situation. The differential signal width is longer than the pulse width when GaAs is exposed to 1 ns~0.2 MeV X ray pulses. The poor signal to noise ratio affects the signal. The excess carrier generation process may be longer than theoretically estimated one under X ray pulse incident situation. The generation process and recombination process of excess carriers in GaAs show very different characteristics compared with optical excitation. The relationship between the system output signal and the incident pulsed radiation depends on the type of the incident radiation. With carefully considering the effects from incident pulse type and transient carriers density, the system can be used to detect ~MeV pulsed radiation. With an upgraded recording module, the system would demonstrate much higher time resolution.

Compact Tunable Laser With InGaAsP Photonic Crystal Nanorods for C-Band Communication

In this study, an ultracompact tunable laser with InGaAsP photonic crystal nanorods for optical communication was demonstrated within 10-μm footprint. The square photonic crystal nanorods with the InGaAsP quantum wells were fabricated and embedded in a flexible polydimethylsiloxane substrate. The high-quality single mode lasing with low threshold around the symmetry point Γ was achieved in experiments. The lasing wavelength can be linearly fine-tuned by varying the extension percentage of photonic crystals and the wavelength tunable range covers the whole conventional band communication ambit. The lasing wavelength shift is attributed to the PhC lattice distortion, and its tuning behavior agrees with the 3-D simulation results. This ultrasmall, wide-range wavelength tunable laser can function as a novel light source for the chip-scale photonic integrated circuits and optics communication system.

Gain-enhanced high-k transmission through metal-semiconductor hyperbolic metamaterials

We analyze the steady-state transmission of high-momentum (high-$k$) electromagnetic waves through metal-semiconductor multilayer systems with loss and gain in the near-infrared (NIR). Using a semi-classical optical gain model in conjunction with the scattering matrix method (SMM), we study indium gallium arsenide phosphide (InGaAsP) quantum wells as the active semiconductor, in combination with the metals, aluminum-doped zinc oxide (AZO) and silver (Ag). Under moderate external pumping levels, we find that NIR transmission through Ag/InGaAsP systems may be enhanced by several orders of magnitude relative to the unpumped case, over a large angular and frequency bandwidth. Conversely, transmission enhancement through AZO/InGaAsP systems is orders of magnitude smaller, and has a strong frequency dependence. We discuss the relative importance of Purcell enhancement on our results and validate analytical calculations based on the SMM with numerical finite-difference time domain simulations.

155-μm VCSEL with polarization-independent HCG mirror on SOI

We designed and fabricated a vertical-cavity surface-emitting laser (VCSEL) incorporating a polarization-independent high-index-contrast subwavelength grating (HCG) mirror on silicon-on-insulator (SOI) for a novel polarization-bistable device on a silicon substrate. The VCSEL consists of the HCG mirror, an active layer with InGaAsP quantum wells having optical gain around 1.55 μm, and an Al0.9Ga0.1As/Al0.16Ga0.84As DBR. We used direct wafer bonding for the bonding between the active layer and the AlGaAs DBR, and benzocyclobutene (BCB) bonding for the bonding between the active layer and the polarization-independent HCG mirror. The reflectivity of the HCG embedded with BCB was measured, resulting in a 200-nm-high reflectivity band with reflectivity higher than 99% and a small polarization dependence of ± 1%. We achieved lasing of the fabricated HCG-VCSEL at 1527 nm under an optical short pulse excitation with an average power of 50 mW (~0.2 mJ/cm2) at 240 K.

Enhanced and suppressed spontaneous emission from a buried heterostructure photonic crystal cavity

We study spontaneous emission control in a buried-heterostructure (BH) photonic crystal (PhC) cavity in which InGaAsP quantum wells (QWs) are embedded in an InP PhC. Spontaneous emission from QW-PhC cavities have been extensively investigated, but they suffer from poor carrier confinement and surface non-radiative recombination. Therefore, the clear spontaneous emission control has been only observed in quantum dots PhC cavities. The present study shows that the BH-QW-PhC cavities can exhibit distinctive spontaneous emission control in QW-PhCs. We observed large emission-rate ratio between the on- and off-resonant conditions of 30:1. This is the highest ratio reported for QW-PhCs.

Transfer-printed stacked nanomembrane lasers on silicon

A hybrid laser that combines silicon photonic-crystal reflectors with transfer-printed InGaAsP quantum wells offers a convenient means of realizing surface-emitting lasers on silicon.

Analysis of linewidth enhancement factor for compressively strained AlGaInAs and InGaAsP quantum well lasers

We have compared and analyzed theoretical investigation for the possibility of extreme reductions in the linewidth enhancement factor (α-factor) in strained layer quantum-well (QW) lasers between AlGaInAs and InGaAsP material. Valence band effective masses and optical gain in both types of QW lasers under compressive strain have been calculated using 4 × 4 Luttinger–Kohn Hamiltonian. We have used Kramers–Kronig relations to calculate the refractive index change due to carrier induced. The α-factor was up to 1.61 times smaller in AlGaInAs QW than in InGaAsP QW laser. The material differential modal gain and carrier induced refractive index change was found to be approximately 1.38 times larger and 1.15 times smaller respectively, in the previous material QW than in the latter QW laser. We also compared our results to the previously reported results for both QWs lasers.

Analysis of using femtosecond laser scanning system to impurity-induced disordering of InGaAsP quantum wells

This study is the first to demonstrate the selectivity quantum well intermixing process by using a femtosecond laser scanning-induced disordering technique. The advantages of the femtosecond laser are photochemical machining and the two-photon absorption mechanism. The femtosecond laser system can convert writing into the scan to create a nanostructure by adjusting the lens. The effect of power on the band gap shift during laser scanning was investigated. The band gap shift was small and unstable without the heating substrate. A wavelength shift higher than 77.3 nm for the InGaAsP MQW material was obtained at elevated temperatures.

Nanobeam photonic bandedge lasers

We demonstrate one-dimensional nanobeam photonic bandedge lasers with InGaAsP quantum wells at room temperature from the lowest dielectric band of photonic crystal nanobeam waveguides. The incident optical power at threshold is 0.6 mW (effectively ~18 μW). To confirm the lasing from the dielectric bandedge, the polarization and the photoluminescent spectra are taken from nanobeams of varying lattice constants. The observed shift of the lasing wavelength agrees well with the computational prediction.

Lambda shifted photonic crystal cavity laser

We propose and demonstrate an alternative type of photonic crystal laser design that shifts all the holes in the lattice by a fixed fraction of the targeted emission wavelength. The structures are realized in InGaAsP (λ=1.15) with InGaAsP quantum wells (λ=1.52) as gain material. Cavities with shifts of 1/4 and 3/4 of the emission wavelength were fabricated and characterized. Measurements show threshold behavior for several modes at room temperature. Both structures are simulated using a finite difference time domain method to identify the resonances in the spectra and calculate the mode volume of the dominant mode.

Gain-assisted propagation of surface plasmon polaritons via electrically pumped quantum wells

We studied the loss compensation of surface plasmon polaritons (SPPs) with InGaAsP quantum wells at telecom wavelength. The quantum wells are buried in the vicinity of a thin Au film. The propagation length of short-range SPPs increases drastically with the gain coefficient of quantum wells, generated by a forward bias. The elongation of SPP propagation is experimentally observed via long-range SPPs, which strongly couple with the short-range SPPs. This study paves a way for electrically manipulated amplification of SPPs in plasmonic circuits.

Room temperature characterisation of InGaAlAs quantum well laser structures using electro‐modulated reflectance and surface photovoltage spectroscopy

AbstractIn this study, two tri‐metal quaternary InGaAlAs quantum well (QW) laser structures grown on InP are compared to a conventional InGaAsP QW structure, also grown on InP, all designed to lase at 1.55 μm. Several spectroscopic methods are used to study the samples including surface photo‐voltage (SPV) and electro‐modulated reflectance (ER). In the tri‐metal samples the ground‐ and two excited‐state QW transitions are detectable in both types of spectroscopy. The SPV and ER give results in agreement to within a few meV of each other. By comparing the position of the measured QW transitions with those predicted theoretically, the conduction band offsets of the tri‐metal samples can be determined and compared to that in the InGaAsP sample. It is found that the tri‐metal samples have a much larger conduction band offset of ∼66% compared to the ∼40% in the InGaAsP sample. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Polarization-selective resonant photonic crystal photodetector

Resonance-assisted photonic crystal (PhC) slab photodetectors are demonstrated by utilizing six 7-nm-thick InGaAsP quantum wells. In order to encourage efficient photon coupling into the slab from the vertical direction, a coupled-dipole-cavity-array PhC structure is employed. Inheriting the characteristics of the dipole mode, this resonant detector is highly polarization selective and shows a 22-nm-wide spectral width. The maximum responsivity of 0.28A∕W, which is >20 times larger than that of the identical detector without the pattern, is observed near 1.56μm.

1 THz Modulation in InGaAsP Multiple Quantum Wells for 40 Gb/s Applications

The terahertz (THz) rate modulation of quantum well (QW) electrooptic modulators necessitates a new way of thinking about how the modulation field modulates light; specifically, an incident narrow-band (with respect to the modulation frequency) signal once modulated acquires frequency components separated from the input signal center frequency by multiples of the modulation frequency. In this paper, we discuss the design of the QWs comprising the modulator to maximize the output at such THz sidebands of the incident optical frequency in InGaAsP QW based devices. We present a theoretical treatment of the case in which the THz modulation frequency is out of resonance between any exci- tonic levels near those exploited for the optical modulation, thus enabling an adiabatic treatment of the modulated optical susceptibility. We show that THz sideband conversion efficiencies of ~1% may be possible.

All-optical bistable switching in curved microfiber-coupled photonic crystal resonators

The authors report low-power optical bistability under continuous wave pumping conditions in five-cell photonic crystal linear resonators containing InGaAsP quantum wells, by employing the fiber-coupling technique. The threshold bistable power is measured to be 35μW at the normalized detuning of −1.724. Owing to the high band-edge nonlinearities of quantum wells and the efficient fiber coupling, minimal instability is observed. In addition, all-optical switching is demonstrated with switching energy less than 75.4fJ.