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Modelocked semiconductor lasers are used to generate a set of phase-locked optical frequencies on a periodic grid. The periodic and phase coherent nature of the optical frequency combs makes it possible for the realization of high...
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Modelocked semiconductor lasers are used to generate a set of phase-locked optical frequencies on a periodic grid. The periodic and phase coherent nature of the optical frequency combs makes it possible for the realization of high-performance optical and RF arbitrary-waveform synthesis. In addition, the resulting optical frequency components can be used for communication applications relying on direct detection, dense wavelength division multiplexing (WDM), coherent-detection WDM, optical time-division multiplexing, and optical code division multiple access. This paper highlights the recent results in the use of optical frequency combs generated from semiconductors for ultrawideband signal processing and communication applications.
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We propose and demonstrate an advanced optical modulation format that makes use of both spectral and temporal phase encodings (2-D) for applications requiring exceptional security. The method combines modulation techniques used in...
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We propose and demonstrate an advanced optical modulation format that makes use of both spectral and temporal phase encodings (2-D) for applications requiring exceptional security. The method combines modulation techniques used in direct-sequence spread-spectrum coding, spectral-phase encoding, and M-ary phase-shift keying with codes generated using cryptographically secure pseudorandom number generators. The wideband transmission signal is very difficult for an eavesdropper to record or analyze. Signal-to-noise ratio limitations imposed by quantum effects enhance the security further. The properties of the transmitted signal make it especially useful for physics-based key expansion systems. We have successfully used this setup to transmit encrypted 155 Mb/s data over 70 km of fiber with a BER value of 4E-5.
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We report, for the first time to our knowledge, the use of graphene as a saturable absorber in an energy-scaled femtosecond Cr~(4+): forsterite laser. By incorporating a multipass cavity, the repetition rate of the original short ...
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We report, for the first time to our knowledge, the use of graphene as a saturable absorber in an energy-scaled femtosecond Cr~(4+): forsterite laser. By incorporating a multipass cavity, the repetition rate of the original short resonator was reduced to 4.51 MHz, which resulted in the generation of 100 fs, nearly transform-limited pulses at 1252 nm with a peak power of 53 kW. To the best of our knowledge, this is the highest peak power obtained from a room-temperature, femtosecond Cr~(4+): forsterite laser mode locked with a graphene saturable absorber. The corresponding pulse energy was 5.3 nJ with only 24 mW of average output power. The saturation fluence and modulation depth of the GSA were measured to be 25 μJ/cm~2 and 0.74%, respectively. The nonlinear effects in the Cr~(4+): forsterite medium that limit further power scaling were also investigated by using different output couplers.
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The well-known Swanepoel's method to calculate the refractive index and the thickness of thin films based on their optical transmission, is only applicable to single facet coated substrates (SFCS), and does not return the correct ...
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The well-known Swanepoel's method to calculate the refractive index and the thickness of thin films based on their optical transmission, is only applicable to single facet coated substrates (SFCS), and does not return the correct values when applied to double facet coated substrates (DFCS). In this work, we present a novel model and an analytical method to characterize the thin film coated on both sides of a substrate. In order to confirm the validity of our novel method, we have fabricated two samples; a DFCS and a SFCS with identical thin films. The thin film on SFCS is analyzed using Swanepoel's method, and the thin films on DFCS are analyzed using our novel method. The refractive index and the thickness value calculated with these two different methods on two different substrates are in agreement with each other and also with the SEM measurements.
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In this work, a 10.287-GHz semiconductor-based harmonically mode-locked laser with 1000 finesse intracavity etalon is demonstrated. The timing jitter integrated from 1 Hz to 100 MHz (Nyquist) is 3 fs (14 fs). The optical linewidth...
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In this work, a 10.287-GHz semiconductor-based harmonically mode-locked laser with 1000 finesse intracavity etalon is demonstrated. The timing jitter integrated from 1 Hz to 100 MHz (Nyquist) is 3 fs (14 fs). The optical linewidth is ~500 Hz and the optical frequency stability is <150 kHz over 30 s.
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We propose a theory and experimentally verify ultraflat comb generation by dual-sine-wave phase-only modulation. This novel approach requires a single optical element and is very practical and efficient in terms of both power budg...
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We propose a theory and experimentally verify ultraflat comb generation by dual-sine-wave phase-only modulation. This novel approach requires a single optical element and is very practical and efficient in terms of both power budget and bandwidth. Using this approach, we have generated two optical spectra, one with 11 comb lines and 1.9-dB flatness and the other with 9 comb lines and 0.8-dB flatness.
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Noise characteristics are studied for a self-stabilized laser utilizing the interplay between the intracavity dispersion and the optical frequency shift. The noise suppression bandwidth of this scheme is from 0 to ~100 KHz and sho...
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Noise characteristics are studied for a self-stabilized laser utilizing the interplay between the intracavity dispersion and the optical frequency shift. The noise suppression bandwidth of this scheme is from 0 to ~100 KHz and showed the reduction of residual timing jitter (integrated from 0.9 Hz to 1 MHz) from 2.2fs to 660 attosecond which represents, to our knowledge, the lowest timing jitter reported for an actively mode-locked laser
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Characterization of the timing and amplitude (AM) noise have shown a greater than 20-dB reduction of the supermode noise spurs from a harmonically mode-locked laser by continuous-wave optical injection. A reduction of the timing j...
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Characterization of the timing and amplitude (AM) noise have shown a greater than 20-dB reduction of the supermode noise spurs from a harmonically mode-locked laser by continuous-wave optical injection. A reduction of the timing jitter and AM noise from 127 to 25 fs and 0.85% to 0.12% (10 Hz–100 MHz), respectively, is demonstrated. A reduction of the optical linewidth, implied by the reduction in the close-in phase noise, is also shown.
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