Marcin Motyka

Bio: Marcin Motyka is an academic researcher from Wrocław University of Technology. The author has contributed to research in topics: Quantum well & Photoluminescence. The author has an hindex of 17, co-authored 102 publications receiving 978 citations.

Monolithic high-index contrast grating: a material independent high-reflectance VCSEL mirror

Abstract: In this paper we present an extensive theoretical and numerical analysis of monolithic high-index contrast grating, facilitating simple manufacture of compact mirrors for very broad spectrum of vertical-cavity surface-emitting lasers (VCSELs) emitting from ultraviolet to mid-infrared. We provide the theoretical background explaining the phenomenon of high reflectance in monolithic subwavelength gratings. In addition, by using a three-dimensional, fully vectorial optical model, verified by comparison with the experiment, we investigate the optimal parameters of high-index contrast grating enabling more than 99.99% reflectance in the diversity of photonic materials and in the broad range of wavelengths.

Fourier Transformed Photoreflectance and Photoluminescence of Mid Infrared GaSb-Based Type II Quantum Wells

Abstract: Fourier-transformed photoreflectance and photoluminescence have been used to study the optical transitions in type II quantum wells (QWs) ranging up to almost 5 µm. High signal-to-noise ratio spectral features resulting from fundamental and excited state transitions have been detected for molecular beam epitaxially grown GaSb/AlSb/InAs/InGaSb/InAs/AlSb/GaSb "W"-shaped QW structures designed for laser-based gas sensing applications in the mid-infrared. The spectral features' dependence on arsenic pressure during growth process and on InAs confining-layer thickness could be followed unambiguously at room temperature.

Contactless electromodulation spectroscopy of AlGaN∕GaN heterostructures with a two-dimensional electron gas: A comparison of photoreflectance and contactless electroreflectance

Abstract: Photoreflectance (PR) and contactless electroreflectance (CER) spectroscopies have been applied to study optical transitions in undoped and Si-doped AlGaN∕GaN heterostructures at room temperature. Spectral features related to excitonic and band-to-band absorptions in GaN layer and band-to-band absorption in AlGaN layer have been resolved and analyzed. In addition, a broad spectral feature related to two-dimensional electron gas has been observed for the Si-doped heterostructure. It has been found that some of the mentioned optical transitions are not observed in CER spectra whereas they are very strong in PR spectra. This phenomenon is associated with different mechanisms of the modulation of built-in electric field in the investigated structure. A combination of PR and CER gives the possibility of a richer interpretation of both PR and CER spectra.

On the deepness of contactless electroreflectance probing in semiconductor structures

Abstract: The deepness of contactless electroreflectance (CER) probing (d CER ) is investigated in this work. CER spectra have been measured for various semiconductor structures and compared with photoreflectance (PR) spectra. It has been shown that most of CER signal origins from the sample region which is very close to the sample surface. It has been found that the d CER is much smaller that the penetration depth of the probing beam (d λ ∼ 0.5-1 μm), d CER « d J . In addition, for samples containing a sheet of carriers (a two dimensional electron gas at an interface or a delta-doped monolayer) the d CER is reduced to the distance from the sample surface to the carrier sheet (e.g. 20 nm). This phenomenon can be called as screening of electromodulation in CER technique. No screening of electromodulation mechanism is observed in PR technique. In addition, the deepness of PR probing (d PR ) is much bigger than the d CER . It means that deeper parts of semiconductor structures (e.g. the buffer layer) can be probed in PR whereas these parts are usually not probed in CER. A different electromodulation mechanism in PR and CER techniques is the origin of various probing deepness for these two techniques. In the case of CER technique, the surface electric field is mainly modulated whereas both surface and interface electric fields can be effectively modulated in the PR technique. In the case of PR technique, the electron-hole pairs can be generated far to the sample surface and hence these carriers can modulate band bending at interfaces which are far to the sample surface, e.g. at the epilayer/buffer interface.

Emission wavelength tuning of interband cascade lasers in the 3–4 μm spectral range

Abstract: GaSb-based type-II quantum well (QW) structures and interband cascade lasers (ICLs) are investigated with regards to the dependence of emission wavelength on active QW thicknesses. Experimentally derived photoluminescence data and electrically driven ICL device data accompanied by theoretical calculations yield an average tuning rate of 0.55 μm per monolayer InAs in the range between 2.97 and 4.16 μm. Together with a temperature dependent ICL tuning behavior of 1.88 nm/K, the presented results provide the means for reliable and accurate emission wavelength control of ICLs in the 3–4 μm wavelength span which is of major importance for gas sensing applications.

Interband cascade lasers

Abstract: We review the current status of interband cascade lasers (ICLs) emitting in the midwave infrared (IR). The ICL may be considered the hybrid of a conventional diode laser that generates photons via electron–hole recombination, and an intersubband-based quantum cascade laser (QCL) that stacks multiple stages for enhanced current efficiency. Following a brief historical overview, we discuss theoretical aspects of the active region and core designs, growth by molecular beam epitaxy, and the processing of broad-area, narrow-ridge, and distributed feedback (DFB) devices. We then review the experimental performance of pulsed broad area ICLs, as well as the continuous-wave (cw) characteristics of narrow ridges having good beam quality and DFBs producing output in a single spectral mode. Because the threshold drive powers are far lower than those of QCLs throughout the λ = 3–6 µm spectral band, ICLs are increasingly viewed as the laser of choice for mid-IR laser spectroscopy applications that do not require high output power but need to be hand-portable and/or battery operated. Demonstrated ICL performance characteristics to date include threshold current densities as low as 106 A cm−2 at room temperature (RT), cw threshold drive powers as low as 29 mW at RT, maximum cw operating temperatures as high as 118 °C, maximum cw output powers exceeding 400 mW at RT, maximum cw wallplug efficiencies as high as 18% at RT, maximum cw single-mode output powers as high as 55 mW at RT, and single-mode output at λ = 5.2 µm with a cw drive power of only 138 mW at RT.

III-nitride semiconductors for intersubband optoelectronics: a review

Abstract: III-nitride nanostructures have recently emerged as promising materials for new intersubband (ISB) devices in a wide variety of applications. These ISB technologies rely on infrared optical transitions between quantum-confined electronic states in the conduction band of GaN/Al(Ga)N nanostructures, namely quantum wells or quantum dots. The large conduction band offset (about 1.8 eV for GaN/AlN) and sub-picosecond ISB relaxation of III-nitrides render them appealing materials for ultrafast photonic devices in near-infrared telecommunication networks. Furthermore, the large energy of GaN longitudinal-optical phonons (92 meV) opens prospects for high-temperature THz quantum cascade lasers and ISB devices covering the 5?10 THz band, inaccessible to As-based technologies due to phonon absorption. In this paper, we describe the basic features of ISB transitions in III-nitride quantum wells and quantum dots, in terms of theoretical calculations, material growth, spectroscopy, resonant transport phenomena, and device implementation. The latest results in the fabrication of control-by-design devices such as all-optical switches, electro-optical modulators, photodetectors, and lasers are also presented.

Compact TDLAS based sensor design using interband cascade lasers for mid-IR trace gas sensing.

Abstract: Two compact TDLAS sensor systems based on different structural optical cores were developed. The two optical cores combine two recent developments, gallium antimonide (GaSb)-based ICL and a compact multipass gas cell (MPGC) with the goal to create compact TDLAS based sensors for the mid-IR gas detection with high detection sensitivity and low power consumption. The sensors achieved minimum detection limits of ~5 ppbv and ~8 ppbv, respectively, for CH4 and C2H6 concentration measurements with a 3.7-W power consumption.

Vertical-cavity surface-emitting lasers for data communication and sensing

Abstract: Vertical-cavity surface-emitting lasers (VCSELs) are the ideal optical sources for data communication and sensing. In data communication, large data rates combined with excellent energy efficiency and temperature stability have been achieved based on advanced device design and modulation formats. VCSELs are also promising sources for photonic integrated circuits due to their small footprint and low power consumption. Also, VCSELs are commonly used for a wide variety of applications in the consumer electronics market. These applications range from laser mice to three-dimensional (3D) sensing and imaging, including various 3D movement detections, such as gesture recognition or face recognition. Novel VCSEL types will include metastructures, exhibiting additional unique properties, of largest importance for next-generation data communication, sensing, and photonic integrated circuits.