Abstract
We report broad bandwidth blue superluminescent light-emitting diodes (SLEDs) based on a short-cavity active region. The dependencies of amplified spontaneous emission (ASE) output power and gain bandwidth on cavity length were investigated in devices whose gain medium consists of a ridge waveguide with embedded InGaN/GaN quantum wells sandwiched between one etched facet coated with a high reflectivity distributed Bragg mirror and one cleaved facet with an anti-reflection coating. 250 μm-long blue SLEDs exhibit a spectral bandwidth up to 7.5 nm at 1.72 mW output power at a wavelength of 427 nm. As cavity length decreases, the bandwidth gradually broadens up to 15 nm for the shortest, 40 μm-long, SLED devices. ASE is confirmed by current-dependent electroluminescence spectra and polarization-dependent emission intensity measurements. The optical features of those short-cavity devices could be helpful for designing broad bandwidth SLEDs aiming for various applications such as optical coherence tomography, next generation displays, on-chip biosensing and imaging.
Highlights
We report broad bandwidth blue superluminescent light-emitting diodes (SLEDs) based on a short-cavity active region
The dependencies of amplified spontaneous emission (ASE) output power and gain bandwidth on cavity length were investigated in devices whose gain medium consists of a ridge waveguide with embedded InGaN/GaN quantum wells sandwiched between one etched facet coated with a high reflectivity distributed Bragg mirror and one cleaved facet with an anti-reflection coating. 250 μm-long blue
superluminescent lightemitting diodes (SLEDs) emitting at short wavelengths with a broad spectral bandwidth could be more favorable for optical coherence tomography (OCT) over high power ones, as the lateral resolution is proportional to λ2 /λ, where λ is the central wavelength and λ is the full width at half maximum (FWHM) of the ASE
Summary
We report broad bandwidth blue superluminescent light-emitting diodes (SLEDs) based on a short-cavity active region. The cavity length is designed to be longer than 500 μm to promote amplified spontaneous emission (ASE), leaving the full width at half maximum (FWHM) to less than nm in InGaN-based SLEDs.[6,7] the situation is different for OCT applications. SLEDs emitting at short wavelengths with a broad spectral bandwidth could be more favorable for OCT over high power ones, as the lateral resolution is proportional to λ2 /λ, where λ is the central wavelength and λ is the FWHM of the ASE spectrum.[8,9] developing broad bandwidth ultrashort cavity devices working at high current density could generate superradiance emission, leading to ultrashort light pulses with duration down to the picosecond.[10]. The device design is guided by a trade-off between optical power and ASE bandwidth:[11,12] the longer the cavity length, the higher the output power at a fixed current density, and the narrower the ASE bandwidth
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