Richard A. Hogg

It is common practice to use an un-pumped, PC containing region of a PCSEL to reduce in-plane optical power loss. We simulate the effect of self-absorption in this un-pumped region on parasitic losses. It is found that the in-plane loss may be zeroed for a suitably thick un-pumped PC region width. However, in such devices, the internal loss no longer has a unique value, and the dependence of the minimum total parasitic loss on a range of parameters is discussed.

This paper presents a coupled-wave analysis of triangular-lattice photonic crystal surface emitting lasers (PCSELs) with transverse magnetic polarization. Six plane waves coupled by Bragg diffraction describe the two-dimensional optical coupling. Resonant mode frequencies are calculated for a lattice of circular holes at various fill factors and compared to the plane-wave expansion method. Analytical equations for coupling constants and mode frequencies are derived, and mode degeneracy as a function of fill factor is examined. Comparision to a square lattice TM mode PCSEL shows improved in-plane 2D coupling. The general equations for arbitrary unit cell dielectric functions are discussed, with predictions of the lasing mode supported by finite device calculations.

Quantum dot-based epitaxially regrown photonic crystal surface emitting lasers are demonstrated at room temperature. The GaAs-based devices, which are monolithically integrated on the same wafer, exhibit ground state lasing at ∼1230 nm and excited state lasing at ∼1140 nm with threshold current densities of 0.69 and 1.05 kA/cm2, respectively.

Probabilistic Markov chain modeling of photonic crystal surface emitting lasers (PCSELs) is reported. This simulation links the scattering parameters of the photonic crystal (PC) and device level losses of the PCSEL. The criteria for the conversion of the numerical model and agreement with data from the literature are discussed. We then explore the effect of increasing PC coupling coefficients and boundary mirror reflectivity on the in-plane power loss from the PCSEL. The effect of spatially varying the boundary reflectivity on the near-field is also explored.

We investigated the stable polarization-pinning properties of substrate emission InGaAs-based 980 nm multi-mode vertical-cavity surface-emitting lasers (VCSELs). For the multi-mode 40 um diameter aperture VCSELs, we introduced 30 μm wide, 9 μm depth deep trenches that are 15 μm away from the cavity aperture. The VCSELs with trench structure produced higher transverse-electric (TE) polarized light output power, as compared with transverse-magnetic (TM) polarized light output power, namely, the effective TM polarization suppression was realized. These trench-etched VCSELs exhibited a 7.5 dB orthogonal polarization suppression ratio with 16.8 mW of light output power at 60 mA of current injection. The dominant TE polarization distribution was observed in polarization-resolved near-field images of spontaneous and stimulated emission due to the induced strain by the etched trenches.

Resilience of 1300nm In(Ga)As/GaAs quantum dot lasers to external optical feedback is systematically investigated from -10 °C to 85 °C. The high-resolution spectral and current-dependent linewidth enhancement factor is measured for all modes in the positive net modal gain region. Complimentary to that, analysis of the free-running and under deployment specific feedback relative intensity noise is discussed in the context of compliance against the IEEE 802.3ah specifications at the full range of temperatures.

Electrochemical voltammetric sensors are some of the most promising types of sensors for monitoring various physiological analytes due to their implementation as non-invasive and portable devices. Advantages in reduced analysis time, cost-effectiveness, selective sensing, and simple techniques with low-powered circuits distinguish voltammetric sensors from other methods. In this work, we developed a Cu₂O-based non-enzymatic portable glucose sensor on a graphene paste printed on cellulose cloth. The electron transfer of Cu₂O in a NaOH alkaline medium and sweat equivalent solution at very low potential (+0.35 V) enable its implementation as a low-powered portable glucose sensor. The redox mechanism of the electrodes with the analyte solution was confirmed through cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy studies. The developed biocompatible, disposable, and reproducible sensors showed sensing performance in the range of 0.1 to 1 mM glucose, with a sensitivity of 1082.5 ± 4.7% µA mM⁻¹ cm⁻² on Cu₂O coated glassy carbon electrode and 182.9 ± 8.83% µA mM⁻¹ cm⁻² on Cu₂O coated graphene printed electrodes, making them a strong candidate for future portable, non-invasive glucose monitoring devices on biodegradable substrates. For portable applications we demonstrated the sensor on artificial sweat in 0.1 M NaOH solution, indicating the Cu₂O nanocluster is selective to glucose from 0.0 to +0.6 V even in the presence of common interference such as urea and NaCl.

Low-temperature photoluminescence spectroscopy (PL) and excitation spectroscopy(PLE) are used to characterize and compare high current density resonant tunnelling diodes (RTD) structures. RTD structural characteristics are detected using X-Ray diffraction (XRD) while the electrical characteristics are detected by PL and PLE. Results are used to link the structure electrical properties to the RTD device IV characteristic. We started focusing the attention on the first quasi bound state (e₁) energy, fundamental for the RTD operation. PL is used to detect the TypeI and Type II QW radiative transitions. The e₁ state is obtained by the difference between the Type I (e₁–hh₁) and type II (conduction band–hh₁) transitions. PLE is consequently used to detect the e2-hh2 transition from which we characterize the energy of the e2 state and its position with respect to the e1 state. Experimental data are confirmed by the RTDs device IV characteristics. We highlight the combination PL and PLE as a powerful, fast, and non-destructive characterization method to link wafer properties and device performance in RTD structures.