SPECTRAL CHARACTERIZATION OF TWO-DIMENSIONAL PHOTONIC CRYSTAL SLABS BY USING MID-INFRARED ANGLE-RESOLVED REFLECTION MEASUREMENT (Seminar Seninan Fisika 11 September 2023)

Departemen Fisika, Fakultas Sains dan Analitika Data (FSAD), Institut Teknologi Sepuluh Nopember (ITS) akan menyelenggarakan kembali kegiatan Seminar Seninan pada minggu ke-3 perkuliahan Semester Gasal 2023/2024 ini, tepatnya pada tanggal 11 September 2023.

Pada Seminar Seninan yang ke-1 ini, anggota dari Laboratorium Optoelektronika dan Elektomagnetika Terapan yaitu Siti Chalimah, M.Si., Ph.D., yang akan menjadi narasumber.

Topik yang akan diangkat dalam kesempatan kali ini adalah “SPECTRAL CHARACTERIZATION OF TWO-DIMENSIONAL PHOTONIC CRYSTAL SLABS BY USING MID-INFRARED ANGLE-RESOLVED REFLECTION MEASUREMENT”.

Kegiatan ini akan dilaksanakan secara luring pada pukul 13.30 s.d. 15.00 WIB, bertempat di Ruang Kelas J-103. Mahasiswa di lingkungan Departemen Fisika wajib menghadiri kegiatan ini dan mengisi lembar kehadiran secara daring dengan cara memindai QR Code yang tersedia di depan pintu masuk Ruang Kelas J-103.

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SEMINAR SENINAN DEPARTEMEN FISIKA FSAD ITS

SPECTRAL CHARACTERIZATION OF TWO-DIMENSIONAL PHOTONIC CRYSTAL SLABS BY USING MID-INFRARED ANGLE-RESOLVED REFLECTION MEASUREMENT

Abstract:

Quantum Cascade Lasers (QCLs), known as novel semiconductor lasers based on intersubband transitions, have been tremendously developed because they can cover broad spectral emission at midinfrared wavelengths and are regarded as one of the most promising laser candidates for gas sensing and analysis. Currently, photonic crystal surface-emitting laser (PCSEL), a new type of semiconductor laser that utilizes photonic crystals integrated on top of the active layer has been applied to QCL resonators which is expected to serve as a way of creating midinfrared lasers with a good beam quality.

In PCSEL, the principle of the laser action relies on the zero-group velocity of light at photonic band edges, which results in strong in-plane feedback inside the PC slab. Moreover, when the band edges are formed at the  point in momentum space, radiation into free space is purely out of the plane, i.e., normal to the slab. Careful PC design that realizes perfect resonance between the band-edge mode and the material gain frequencies is essential for achieving vertical emission and the measurement of in-plane dispersion relation is frequently performed to verify optimum conditions in fabricated devices.

A technique commonly used to characterize in-plane dispersion relations (photonic band structures) in visible and near-infrared wavelength PCSEL devices is the angle-resolved observation of subthreshold luminescence spectra. However, this technique cannot be used for mid-infrared wavelengths due to the limited sensitivity of infrared detectors. Thus, an alternative scheme is required for characterizing the PC slabs. We developed a high-resolution angle-resolved reflection measurement technique to observe photonic band structures in the vicinity of the  point. We applied this technique to the study of standard silicon-on-insulator (SOI) based triangular-lattice PC slabs that have C6v-symmetry. We successfully assigned the eigenmode symmetry and clarified the formation of the photonic Dirac cone, which was materialized by the effective degeneracy of the  point modes. We applied our technique to the characterization of actual PCSEL devices formed of In(Ga, Al)As/InP-based QCL multilayer structures. We studied a variety of PC slabs that have different shapes and filling factors. In particular, we compared the reflection spectra for the sample with C4v-symmetry and that with symmetry lower than C4v. The results imply that the lower symmetry PC slabs enable efficient light extraction.

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