719 research outputs found
Variable repetition frequency femtosecond-pulse surface emitting semiconductor laser
No full textWe report a femtosecond-pulse vertical-external-cavity surface-emitting laser with a continuous repetition frequency tuning range of 8% near 1 GHz. A constant average output power of 56?±?1 mW and near-transform-limited pulse duration of 450?±?20 fs were observed across the entire tuning rang
Spectral gain and cavity loss characterization of an optically-pumped external-cavity surface-emitting quantum well laser
No full textWe present the spectral gain and cavity loss characterisation of an optically-pumped external-cavity 1-µm surface-emitting InGaAs quantum well laser by observing the evolution of intracavity power and spontaneous emission following the uncovering of the cavity mode by an intra-cavity chopper. The smooth monotonic rise (fall) is characteristic of an external-cavity quantum well laser where the photon lifetime is approximately two orders of magnitude higher than the carrier lifetime
Fluence and polarisation dependence of GaAs based Lateral Photo-Dember terahertz emitters
No full textWe characterise THz output of lateral photo-Dember (LPD) emitters based on semi-insulating (SI), unannealed and annealed low temperature grown (LTG) GaAs. Saturation of THz pulse power with optical fluence is observed, with unannealed LTG GaAs showing highest saturation fluence at 1.1 ± 0.1 mJ cm-2. SI-GaAs LPD emitters show a flip in signal polarity with optical fluence that is attributed to THz emission from the metal-semiconductor contact. Variation in optical polarisation affects THz pulse power that is attributed to a local optical excitation near the metal contact
Investigation of the role of the lateral photo-Dember effect in the generation of terahertz radiation using a metallic mask on a semiconductor
No full textPulses of coherent terahertz radiation can be efficiently generated by a lateral diffusion current after ultrafast generation of photo-carriers near a metal interface on the surface of a semiconductor, this is known as the lateral photo-Dember effect. We investigate how the emission depends on the pump spot position, size, power and how it is affected by the application of an applied external bias. We study the role of the metallic mask and how it suppresses emission from the carriers diffusing under it due to a reduction of available radiation states both theoretically and experimentally.<br/
H.E. Rainier letter to the Equal Suffrage League, September 9, 1914
No full textH.E. Rainier wrote this letter on September 9, 1914, addressed to the Equal Suffrage League, to inform the League of a debate Rainier would be participating in. Rainier requested facts and statistics that would help support women's suffrage in the debate on the issue of equal suffrage. Rainier requested statistics especially on the rates of divorce in states that had already achieved suffrage for women.
The Franklin County Woman Suffrage Association was formed in 1912, after the Ohio Constitutional Convention elected to bring to a vote the question of removing the words "white male" from the state constitution with regard to voting rights. Headquartered in the Chamber of Commerce building in Columbus, Ohio, the organization put out regular publications, organized public speeches and meetings, distributed literature and held parades in support of the suffrage movement. Women's suffrage in Ohio was defeated in a special election in 1912 and again in 1914 and 1916 before a resolution narrowly passed in 1917 allowing municipal voting by women in Columbus. In 1920, the 19th Amendment passed, extending the vote to women and prohibiting state and federal government from denying suffrage on the basis of sex
4.35 kW peak power femtosecond pulse mode-locked VECSEL for supercontinuum generation
No full textWe report a passively mode-locked vertical external cavity surface emitting laser (VECSEL) producing 400 fs pulses with 4.35 kW peak power. The average output power was 3.3 W and the VECSEL had a repetition rate of 1.67 GHz at a center wavelength of 1013 nm. A near-antiresonant, substrate-removed, 10 quantum well (QW) gain structure designed to enable femtosecond pulse operation is used. A SESAM which uses fast carrier recombination at the semiconductor surface and the optical Stark effect enables passive mode-locking. When 1 W of the VECSEL output is launched into a 2 m long photonic crystal fiber (PCF) with a 2.2 mu m core, a supercontinuum spanning 175 nm, with average power 0.5 W is produced. (C)2013 Optical Society of America</p
Passively harmonically mode-locked vertical-external-cavity surface-emitting laser emitting 1.1 ps pulses at 147 GHz repetition rate
No full textCoupled-cavity passive harmonic mode-locking of a quantum well based vertical-external-cavity surface-emitting laser has been demonstrated, yielding an output pulse train of 1.5 ps pulses at a repetition rate of 80 GHz and with an average power of 80 mW. Harmonic mode-locking results from coupling between the main laser cavity and a cavity formed within the substrate of the saturable absorber structure. Mode-locking on the second harmonic of the substrate cavity allows a train of 1.1 ps pulses to be generated at a repetition rate of 147 GHz with 40 mW average power
Jain–Kivelson-type resonance as a noninvasive probe of screening in the quantum Hall regime
No full textMaterial parameter extraction in THz-TDS using a converging beam transfer function
No full textWe demonstrate a parameter extraction algorithm based on a theoretical transfer function, which takes into account a converging THz beam. Using this, we successfully extract material parameters from data obtained for a quartz sample with a THz time domain spectrometer.</p
High peak power femtosecond pulse VECSELs for terahertz time domain spectroscopy
No full textWe report on a high peak power femtosecond modelocked VECSEL and its application as a drive laser for an all semiconductor terahertz time domain spectrometer. The VECSEL produced near-transform-limited 335 fs sech2 pulses at a fundamental repetition rate of 1 GHz, a centre wavelength of 999 nm and an average output power of 120 mW. We report on the effect that this high peak power and short pulse duration has on our generated THz signal.</p
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