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Mohammad Tahsin Alam

Publications and source records attributed to Mohammad Tahsin Alam.

2 recordsLinked to original sources

Tamm Plasmon--Enhanced Widely Tunable Near-Infrared Nanolaser with Superior Efficiency and Output Power

Plasmonic resonances enable strong electromagnetic field confinement and have been widely exploited in plasmonic nanolasers, particularly through surface plasmon polaritons and localized surface plasmons. However, their performance is often limited by bidirectional output coupling and multimode far-field emission, primarily due to higher-order diffraction arising from these modes. In this work, we utilize the Tamm plasmon resonance to realize lasing in the NIR region with wide tunability. The optical Tamm states are excited at the metal-DBR interface by an incident pump pulse and their emission intensity is significantly enhanced via extraordinary optical transmission through a metallic nanohole array. The subwavelength periodicity of the nanohole array restricts the emission to the zeroth order, resulting in a highly directional far-field pattern with a full width at half maximum of approximately 0.631 degrees. To further improve performance, a second DBR is incorporated beneath the pump side, which substantially suppresses backward emission around the lasing wavelength and enhances forward lasing intensity by around 1.3 X 10^4 times, thus increasing the integrated emission power. The combination of Tamm plasmon excitation and dual-DBR feedback significantly improves the cavity's optical response and overall lasing efficiency. Additionally, we have demonstrated lasing at 870 nm with a reduced pump threshold of 2.8 X 10^7 V/m (energy of 0.0031 mJ/cm^2). Moreover, a broad tunability in lasing wavelength, spanning from 850 nm to 944.5 nm, is achieved. These results demonstrate a cost-effective and versatile strategy for plasmonic nanolasers with enhanced output power, low reflection-side loss, wide tunability, and strong integration potential for on-chip photonic and quantum technologies.

physics.optics↗

Developing a Cost-Effective Spectrometer: A Practical Approach

The paper demonstrates the design and execution of a low-cost optical spectrometer that employs a webcam, diffraction grating & Python (a free, open-source programming language). The device's design prioritized economy and usability, with a black box casing to reduce stray light and increase measurement accuracy. A diffraction grating made from a DVD was used to split light into its constituent wavelengths, which were then collected by the camera. The calibration procedure used a RED TIDE USB650 Fiber Optic Spectrometer to set calibration values for various wavelength ranges, which ensured that the spectrometer's results closely matched those derived from the former, a high-cost industry-standard model. Spectrums of several light sources, such as red, green, blue, yellow, white, magenta, orange, and UV LEDs, as well as a green laser, were studied and compared. The results showed a high level of precision, with minimal divergence from industry-standard spectrometer measurements. This comparison was carried out utilizing Origin software, which allowed for extensive analysis and display of the spectrum data. In addition, the spectrometer captured data in real time, allowing users to watch live spectrum changes and ensure instant accessibility of results. Despite its simplicity and low cost, the spectrometer provides significant value for instructional and practical applications, making it a valuable tool in cost-constrained situations.

physics.optics↗