Takuya Hirano

Wideband, highly noise-suppressed squeezing was observed by using a high-speed, high-quantum-efficiency light-emitting diode. The squeezing bandwidth extended over 200 MHz. We also have investigated the dependence of the squeezing bandwidth on the pump-current at low temperature. The experimental result was compared with the theoretical predictions based on a unified model of the pump and recombination process and was well explained by the model at the thermionic emission limit. (C) 2000 Optical Society of America.

Wideband, highly noise-suppressed squeezing was observed by using a high-speed, high-quantum-efficiency light-emitting diode. The squeezing bandwidth extended over 200 MHz. We also have investigated the dependence of the squeezing bandwidth on the pump-current at low temperature. The experimental result was compared with the theoretical predictions based on a unified model of the pump and recombination process and was well explained by the model at the thermionic emission limit. (C) 2000 Optical Society of America.

発光ダイオードやレーザーダイオードのような半導体発光素子を使うと,光子数揺らぎが標準量子限界よりも小さな光(サブポアゾン光)を比較的容易に発生することができる.近年,得られるサブポアゾン化の度合いや安定性などが大幅に向上し,それに伴ってサブポアゾン光発生の物理機構,特に素子内のキャリアダイナミクスとの密接な関係なども明らかになってきた.本稿では,応用も念頭においてサブポアゾン光発生の意味と研究の現状を紹介する.

We utilized a blue-detuned Laguerre-Gaussian (doughnut) laser beam to trap cold rubidium atoms by optical dipole force. "Pulsed" polarisation gradient cooling was applied to the trapped atoms to suppress the trap loss due to heating caused by random photon scattering of the trapping light. In this trap about 10(8) atoms were initially captured and the trap lifetime was 1.5 s, which was consistent with losses due to background gas collisions. This trap can readily be applied to atom guiding, compression, and evaporative cooling.

We utilized a blue-detuned Laguerre-Gaussian (doughnut) laser beam to trap cold rubidium atoms by optical dipole force. "Pulsed" polarisation gradient cooling was applied to the trapped atoms to suppress the trap loss due to heating caused by random photon scattering of the trapping light. In this trap about 10(8) atoms were initially captured and the trap lifetime was 1.5 s, which was consistent with losses due to background gas collisions. This trap can readily be applied to atom guiding, compression, and evaporative cooling.

We demonstrate experimental results on the generation of sub-Poissonian photon fluxes emanating from an AlGaAs light-emitting diode, which manifest a wide-band (0-100 MHz) noise suppression below the standard quantum limit level despite low current density (similar to 38 A/cm(2)) operation at room temperature. The experimental noise power spectrum is well fitted in terms of the theoretical curve estimated with the quantum mechanical Langevin equations. (C) 1998 American Institute of Physics.

We demonstrate experimental results on the generation of sub-Poissonian photon fluxes emanating from an AlGaAs light-emitting diode, which manifest a wide-band (0-100 MHz) noise suppression below the standard quantum limit level despite low current density (similar to 38 A/cm(2)) operation at room temperature. The experimental noise power spectrum is well fitted in terms of the theoretical curve estimated with the quantum mechanical Langevin equations. (C) 1998 American Institute of Physics.

We have observed more than 3 dB squeezing in photon number fluctuations from a light emitting diode (LED) at liquid nitrogen temperature. The noise reduction is uniform within our measurement bandwidth of 1MHz, and its amount agrees with the emission efficiency of the LED. To our knowledge, it is the largest squeezing ever observed using a LED.

We have observed more than 3 dB squeezing in photon number fluctuations from a light emitting diode (LED) at liquid nitrogen temperature. The noise reduction is uniform within our measurement bandwidth of 1MHz, and its amount agrees with the emission efficiency of the LED. To our knowledge, it is the largest squeezing ever observed using a LED.

We review our experimental result on the generation of sub-Poissonian photon fluxes from high-speed light emitting diodes (LEDs) driven by high-impedance constant-current sources and present our new scheme on the basis of Stark-effect blockade of photon emissions. The experiments demonstrate a large noise-suppression of spontaneous photon stream, 3.1 dB below the standard quantum limit level at 80 K and increasing bandwidth (3-16 MHz) for the noise-suppression with increasing pump current (50 mu A-5 mA) at room temperature. The latter has been clearly interpreted in terms of the distinctive contribution of collective Coulomb-blockade for pump events and of recombination dynamics to the bandwidth. The basic physics behind the proposed scheme is illustrated, theoretically demonstrating, as a consequence of the coexistence of the Stark-effect-and Coulomb-blockade, 4.5 dB-noise-suppression to below the standard quantum limit level in a tailor-made diode driven by a constant voltage source. (C) 1997 Elsevier Science S.A.

We have investigated the intensity squeezing bandwidth of sub-Poissonian light generated by a high-speed light-emitting diode. The squeezing bandwidth of a constant-current-driven light-emitting diode is proportional to a driving current in a lower-current regime and approaches a constant in a higher-current regime. This dependence on driving current is well explained by the contributions of the thermionic emission time and the radiative lifetime to the squeezing bandwidth. (C) 1997 Optical Society of America.

We have constructed a novel optical trap for neutral atoms by using a Laguerre-Gaussian (doughnut) beam whose frequency is blue detuned to the atomic transition. Laser-cooled rubidium atoms are trapped in the dark core of the doughnut beam with the help of two additional laser beams which limit the atomic motion along the optical axis. About 10(8) atoms are initially loaded into the trap, and the lifetime is 150 ms. Because the atoms are confined at a point in a weak radiation field in the absence of any external field, ideal circumstances are provided for precision measurements. The trap opens the way to a simple technique for atom manipulation, including Bose-Einstein condensation of gaseous atoms.

We have investigated the intensity squeezing bandwidth of sub-Poissonian light generated by a high-speed light-emitting diode. The squeezing bandwidth of a constant-current-driven light-emitting diode is proportional to a driving current in a lower-current regime and approaches a constant in a higher-current regime. This dependence on driving current is well explained by the contributions of the thermionic emission time and the radiative lifetime to the squeezing bandwidth. (C) 1997 Optical Society of America.

We have constructed a novel optical trap for neutral atoms by using a Laguerre-Gaussian (doughnut) beam whose frequency is blue detuned to the atomic transition. Laser-cooled rubidium atoms are trapped in the dark core of the doughnut beam with the help of two additional laser beams which limit the atomic motion along the optical axis. About 10(8) atoms are initially loaded into the trap, and the lifetime is 150 ms. Because the atoms are confined at a point in a weak radiation field in the absence of any external field, ideal circumstances are provided for precision measurements. The trap opens the way to a simple technique for atom manipulation, including Bose-Einstein condensation of gaseous atoms.

We show that a chaotic pulsation in the passive Q-switched CO2 laser system can be made to synchronize to its prerecorded history. A signal based only on the prerecorded history is used to modulate the saturable absorber instead of the actual difference between the prerecorded signal and the current signal. Numerical calculation shows that the synchronization also occurs even if the modulation signal is modified to be the on-off signal.

We show that a chaotic pulsation in the passive Q-switched CO2 laser system can be made to synchronize to its prerecorded history. A signal based only on the prerecorded history is used to modulate the saturable absorber instead of the actual difference between the prerecorded signal and the current signal. Numerical calculation shows that the synchronization also occurs even if the modulation signal is modified to be the on-off signal.

Correlation measurements of the outputs of a nondegenerate optical parametric amplifier with weak coherent input light were performed. By choosing the relative phase between the input and pump light, we observed positive and negative correlation between the signal and idler photons.