Abstract Large-area lasers are practical for generating high output powers. However, this often comes at the expense of lower beam quality due to the introduction of higher-order modes. Here, we experimentally demonstrate a new type of electrically pumped, large-area edge-emitting lasers that exhibit a high power emission (∼0.4 W) and a high-quality beam (M 2 ∼1.25). These favorable operational characteristics are enabled by establishing a quasi PT-symmetry between the second-order mode of a large area two-mode laser cavity and that of a single-mode auxiliary partner cavity, i.e., by implementing a partial isospectrality between the two coupled cavities. This in turn enlarges the effective volume of the higher-order modes. As a result, a selective pump applied via current injection into the main laser cavity can provide a stronger modal gain to the fundamental mode, and thus lead to lasing in the single mode regime after filtering out higher order transverse modes. The reported experimental results confirm this intuitive picture and are in good agreement with both theoretical and numerical analysis. Above all, the employed material platform and fabrication process are compatible with the industrial standards of semiconductor lasers. This work provides the first clear demonstration, beyond previous proof-of-concept studies, of the utility of PT-symmetry in building laser geometries with enhanced performance and, at the same time, useful output power levels and emission characteristics.
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Detuned-Structure-Based Beam-Driven Accelerator
An experimental research is being conducted at the Yale University Beam Physics Laboratory, aiming to confirm fundamental aspects of an as-yet untested two-beam collinear electron accelerator concept employing a detuned bimodal cavity structure. The features of this novel beam-driven accelerator concept include (i) interleaving of bunches of the low-current accelerated beam with bunches of the high-current drive beam, while both beams move along the same central axis in the structure; (ii) excitation by the drive beam of two modes of each cavity in the structure, with the frequency of the higher mode equal to three times the frequency of the fundamental TM010mode; and (iii) detuning of the cavity modes away from the frequency of the accelerated and drive beam bunches, and their third harmonic. Advantages that are anticipated from this approach include (a) operation at higher acceleration gradient with lower breakdown and pulsed heating rates than for a structure of single-mode cavities at the same acceleration gradient, due to the unconventional spatiotemporal field distributions in the bimodal cavities; (b) realization of a transformer ratio well above two, due to the detuning of the cavity modes; and (c) greater system simplicity and lower cost than for a two-beam accelerator with separate drive and accelerated beam-lines. The recent R&D; progress is presented.
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- Award ID(s):
- 1632588
- NSF-PAR ID:
- 10110128
- Date Published:
- Journal Name:
- 18th Advanced Accelerator Concepts Workshop (AAC 2018)
- Page Range / eLocation ID:
- 1 to 5
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Encasing an OLED between two planar metallic electrodes creates a Fabry–Pérot microcavity, resulting in significant narrowing of the emission bandwidth. The emission from such microcavity OLEDs depends on the overlap of the resonant cavity modes and the comparatively broadband electroluminescence spectrum of the organic molecular emitter. Varying the thickness of the microcavity changes the mode structure, resulting in a controlled change in the peak emission wavelength. Employing a silicon wafer substrate with high thermal conductivity to dissipate excess heat in thicker cavities allows cavity thicknesses from 100 to 350 nm to be driven at high current densities. Three resonant modes, the fundamental and first two higher harmonics, are characterized, resulting in tunable emission peaks throughout the visible range with increasingly narrow bandwidth in the higher modes. Angle resolved electroluminescence spectroscopy reveals the outcoupling of the TE and TM waveguide modes which blue-shift with respect to the normal emission at higher angles. Simultaneous stimulation of two resonant modes can produce dual peaks in the violet and red, resulting in purple emission. These microcavity-based OLEDs employ a single green molecular emitter and can be tuned to span the entire color gamut, including both the monochromatic visible range and the purple line.
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1109/AAC.2018.8659386
