Quasiparity‐Time Symmetric Microdisk Laser

Abstract

Recent developments in parity‐time (PT) symmetric systems have ushered in unique photonic devices with enhanced functionalities. While single‐mode laser emission has been demonstrated in such systems, the current designs face severe challenges in applications, either due to their stringent requirement on fabrication precision or nonscalability to larger devices. Here, we demonstrate a general mechanism to achieve single‐mode lasing in coupled cavities, which relies on external mode coupling and overcomes these drawbacks. We find significant gain enhancement for selected modes by external coupling, and our experiments have confirmed the resulting single‐mode laser emission in size‐mismatched photonic molecules (PMs), when only one constituent cavity is pumped. This behavior persists for a wide range of pump power, from transparent threshold to gain saturation, and it is highly tolerant of fabrication imprecisions. In addition, the output intensity of such single‐mode lasers also displays enhancement when compared with the same PMs under uniformly pumping. We believe our results will both advance the understanding of different coupling scenarios in coupled cavities and improve the characteristics of onchip laser sources for practical applications.

Anomalies in light scattering

“…In both works, undesired longitudinal modes of microrings have been filtered out to achieve single-mode lasing. A similar method can be utilized to filter transverse modes of multimode cavities as demonstrated in large area microring lasers [127] as well as in stripe lasers [161] and microdisc lasers [162].…”

Transporting the Optical Chirality through the Dynamical Barriers in Optical Microcavities

“…The samples were fabricated with standard photoresist SU8 film doped with 0.8% Rhodamine B in weight . After 10 min exposure in ultraviolet light, a 300 nm PMMA film was spin‐coated onto the SU8 film.…”

“…The samples were fabricated with standard photoresist SU8 film doped with 0.8% Rhodamine B in weight. [31,32] After 10 min exposure in ultraviolet light, a 300 nm PMMA film was spin-coated onto the SU8 film. The cavities were patterned with electronbeam lithography and developed in MIBK for 50 s. Then a 100 nm silica film was evaporated and lifted off using PG remover, leaving a silica mask on the SU8 film.…”

Non-Hermiticity and conservation of orthogonal relation in dielectric microcavity

“…On the other hand, a non-Hermitian system, which is related to openness has complex eigenvalues and its eigenvectors satisfy the bi-orthogonal relation. Recently, various non-Hermitian systems and their properties have been extensively studied theoretically as well as experimentally [1][2][3][4][5][6][7], especially in the fields of avoided resonance crossings (ARCs) [8][9][10][11][12][13][14][15], exceptional points (EPs) [16][17][18], PT-symmetric Hamiltonian systems [19][20][21][22], phase rigidity [23], bi-orthogonal relations [24][25][26][27], and optical chirality around the EP [28][29][30]. Since the Hermitian system and the non-Hermitian system has quite different properties to each other, they are often considered being distinct and independent from each other.…”