Storage Of Light Pulses Research Articles

Putting quantum memories on ice

A new idea for 'freezing-out' unwanted losses in an atomic memory could make it possible to store light pulses on-chip for several minutes, increasing the capability of optical quantum computing.

Proposed nano-scale sensing transducer using nano-waveguide for dynamic measurement applications

We propose a new concept of a nano-sensing transducer system using a nano-waveguide. The small change in physical quantity affects to the change in device parameters such as refractive index or length which is relatively absorbed and observed by the resonant signal. In principle, the stored light pulse at the specified wavelength is generated by using a soliton propagating within the input ring resonators, whereas a resonant signal can be stored within the nano-waveguide, i.e. a transducer, which is formed the sensing ring device. The induced change in the resonant signal is occurred, and can be detected by using the wavelength domain detector (optical spectrum analyzer). Such a proposed device is suitable to perform the measurements in the nano-scale regime such as force, stress and temperature.

Optimizing the retrieval efficiency of stored light pulses

We study the retrieval efficiency of stored light pulses based on electromagnetically induced transparency in multiple simultaneously driven Lambda-systems. The light pulses are stored in coherences between different Zeeman states of laser-cooled atoms. When the stray magnetic field from the environment is minimized by compensation coils we observed a smaller retrieved probe pulse amplitude than for a small externally applied magnetic field, i.e., a seemingly shorter coherence time. We identify this effect as a beating of several coherences due to a very small uncompensated dc magnetic stray field. By intentionally applying a small magnetic field larger than this stray field we were able to increase the retrieved probe pulse amplitude up to five-fold to the value determined by the true coherence time of our system.

Low-light-level all-optical switching based on stored light pulses

Low-light-level all-optical switching based on stored light pulses

Electro-optic control of atom-light interactions using Rydberg dark-state polaritons

We demonstrate a multiphoton Rydberg dark resonance where a $\ensuremath{\Lambda}$ system is coupled to a Rydberg state. This $\mathcal{N}$-type level scheme combines the ability to slow and store light pulses associated with long-lived ground-state superpositions with the strongly interacting character of Rydberg states. For the $n{d}_{5/2}$ Rydberg state in $^{87}\text{R}\text{b}$ (with $n=26$ or 44) and a beam size of 1 mm, we observe a resonance linewidth of less than 100 kHz in a room-temperature atomic ensemble limited by transit-time broadening. The resonance is switchable with an electric field of order $1\text{ }\text{V}\text{ }{\text{cm}}^{\ensuremath{-}1}$. Applications in electro-optic switching and photonic phase gates are discussed.

Quantum coherent control of ultrashort laser pulses

The effective photonic control is one of the key issues in photo-physics. Significant advancement in photonic crystals, quantum optics, ultrafast optics as well as micro-nano-optics gives rise to new opportunities to manipulate the emission and propagation in optical fields, leading to a number of new and interesting discoveries, e.g., ultrashort light pulse storage and efficient energy conversion. This paper reviews the latest research progress in storage, release and energy conversion for ultrashort laser pulses in periodical arrays of absorbing medium. Techniques to fabricate such devices are also presented.

Dynamic Photonic Crystals

When dynamic behaviors are introduced into photonic crystal systems, fascinating new possibilities emerge. For example, the bandwidth of a pulse can be completely compressed to zero, resulting in on-chip all-optical stopping and storage of light pulses. The pulse spectrum can also be inverted around a center frequency to time-reverse an optical pulse.

Manipulating the retrieved frequency and polarization of stored light pulses

We have experimentally demonstrated that stored and retrieved light pulses have different frequencies but maintain phase coherence; a stored light pulse is released with a different polarization. However, the manipulation process causes an energy loss of the retrieved pulse. We have discovered that Clebsch-Gordan coefficients among the Zeeman sublevels play an important role in the energy loss and have demonstrated a solution for avoiding the energy loss.

Manipulating the retrieved width of stored light pulses

We have systematically studied the method proposed by Patnaik et al. [Phys. Rev. A 69, 035803 (2004)] that manipulates the retrieval of stored light pulses. The measured probe pulse width of the retrieval is inversely proportional to the intensity of the reading field. We also show that the method does not introduce any phase shift or jump into the retrieved pulses. Our study demonstrates that the distortion at the output of the light storage can be corrected by manipulating the retrieval process and the phase information of the stored pulses can remain intact during the process.

Coupled Resonator Optical Waveguides: Toward the Slowing and Storage of Light

The development of a simple, solid-state-based technology to slow the propagation of light could prove an important step in the realization of the high-bit-rate communication systems of the future. The use of coupled resonator optical waveguides (CROWs) as practical elements to slow and store light pulses is one possibility.

Manipulating the retrieval of stored light pulses

We consider storage and retrieval of light based on electromagnetically induced transparency in an atomic medium using nonadiabatic switching of a control field. We derive various conditions for writing (and reading) the light information to (and from) the atomic coherence. We obtain an analytical solution for the retrieval of the stored pulse that is in excellent agreement with the full numerical results. We identify the origin of distortion at the output and derive a condition to correct the distortions by manipulating the retrieval process.

Observation of Ultraslow and Stored Light Pulses in a Solid

We report ultraslow group velocities of light in an optically dense crystal of Pr doped Y2SiO5. Light speeds as slow as 45 m/s were observed, corresponding to a group delay of 66 micros. Deceleration and "stopping" or trapping of the light pulse was also observed. These reductions of the group velocity are accomplished by using a sharp spectral feature in absorption and dispersion that is produced by resonance Raman excitation of a ground-state spin coherence.

Optical resonator matching for JAERI free electron laser

An optical resonator length of free electron lasers must be exactly matched with the frequency of the repeated electron beam from the accelerator driver so the incident electron beam can overlap with stored light pulses in the resonator. We made the exact resonator length matching by injecting ultrashort laser light pulses in the resonator as external clock signals. The external laser was a mode-locked Ti:Sapphire laser with 80 fs pulse width and synchronized with the accelerator clock signals. With the simultaneous use of a streak camera and a photo diode, we succeeded in making the quick matching within an accuracy of 1 μm or less in a direct and exact manner.

Temporal behaviour and longitudinal instabilities on the Super-ACO free electron laser

In a Free Electron Laser (FEL) the amplification of a stored light pulse varies according to different conditions of gain. This implies, for a Storage Ring FEL (SRFEL), a particular behaviour of the temporal structure. Measurements of the temporal width of the laser pulse in the Super-ACO FEL versus stored ring current and versus the so called “detuning” have been performed with a dissector. The results presented here show how the temporal width is influenced by the evolution of the gain. The position of the laser pulse with respect to the center of the positron bunch in equilibrium condition has been also measured. These results seem to confirm, along with the existence of longitudinal instabilities of the laser pulse for a perfect synchronisation, the important role played by detuning in SRFEL saturation process.