Picosecond Electro-optic Sampling Research Articles

Phase-locked-loop-based delay-line-free picosecond electro-optic sampling system

A delay-line-free, high-speed electro-optic sampling (EOS) system is proposed by employing a delay-time-controlled ultrafast laser diode as the optical probe. Versatile optoelectronic delay-time controllers (ODTCs) based on modified voltage-controlled phase-locked-loop phase-shifting technologies are designed for the laser. The integration of the ODTC circuit and the pulsed laser diode has replaced the traditional optomechanical delay-line module used in the conventional EOS system. This design essentially prevents sampling distortion from misalignment of the probe beam, and overcomes the difficulty in sampling free-running high-speed transients. The maximum tuning range, error, scanning speed, tuning responsivity, and resolution of the ODTC are 3.9π (700°), <5% deviation, 25–2405 ns/s, 0.557 ps/mV, and ∼1 ps, respectively. Free-running wave forms from the analog, digital, and pulsed microwave signals are sampled and compared with those measured by the commercial apparatus.

半導体レーザを用いたピコ秒非接触E-Oサンプリング

半導体レーザを用いたピコ秒非接触E-Oサンプリング

Transient nonlinear optical properties of δ-doped asymmetric superlattices measured by picosecond electro-optic sampling

We have performed the first picosecond time-resolved measurements of the photorefractive and nonlinear absorptive properties of asymmetric GaAs doping superlattices. The lack of inversion symmetry in these structures results in a net photoinduced electric field and, therefore, photorefractive phenomena via the χ(2) of the material. Using the electro-optic sampling technique, the temporal behavior of the photorefractive, and nonlinear absorption effects are uniquely determined. We have observed peak refractive index changes of 3.8×10−4 at an energy density of 40 fJ/μm2.

40 GHz measurement on InP/air gap line by picosecond electro-optic sampling

An electro-optic sampling technique has been used to study an air gap microstrip line deposited on a semi-insulating InP substrate at frequencies up to 40 GHz. The 1 ps light pulses are obtained from a compressed mode locked Nd:YAG laser with a rubidium clock as a phase reference. The air gap line is compatible with III-V compound fabrication technology and can be used as an alternative to classical microstrip or coplanar plane wave interconnection techniques used in high speed devices. High frequency operation of this type of line does not require any thinning of the substrate and the effective dielectric constant is reduced by a factor of more than 3 compared with the dielectric constant of the substrate.

Picosecond electro-optic sampling of electron-hole vertical transport in surface space charge fields

The longitudinal electro-optic effect in GaAs(100) is used to measure the dynamics of electron-hole pair separation in surface space charge fields present at GaAs/oxide interfaces. At low photocarrier injection, the rise time in the E field transient is a direct measurement of the charge transport across the space charge field which is found to be faster than 500 fs. The results demonstrate that the charge carriers are energetically unthermalized at the surface prior to the surface chemistry. This method is also found to be sensitive to 10 −5 of a monolayer of charged surface states.

Novel method for ultrahigh-frequency electro-optic time-domain reflectometry

We propose a new approach to time-domain reflectometry utilising picosecond electro-optic sampling and counter-propagating electrical pulses on a coplanar transmission line. This method enables direct acquisition of the incident and reflected waveforms at the interface between a device and transmission line without requiring temporal separation between the waveforms or deconvolution of the effect of the transmission line on the waveforms.

Measurement of on-chip waveforms and pulse propagation in digital GaAs integrated circuits by picosecond electro-optic sampling

We demonstrate precise measurement of sub-100 ps rise time on-chip electrical waveforms and of pulse propagation in digital GaAs integrated circuits with the use of picosecond electro-optic sampling. These experiments yield the first non-invasive measurement of single-gate propagation delays via direct and precise observation of on-chip waveforms at the input and output of individual logic gates internal to an integrated circuit.

An application of picosecond electro-optic sampling to superconducting electronics

A picosecond electro-optic sampling technique has been used to measure the switching threshold of a single tunnel junction in a coplanar transmission line geometry. The optical system used, a colliding-pulse mode-locked laser, generated two 120 fs FWHM at 100 MHz. One pulse was used, via a photoconductive switch, to generate an electrical signal of adjustable height and width. The second pulse was used to detect the electrical transient by probing the change in the birefringence of a lithium tantalate crystal induced by the electrical signal. This optical sampling scheme had intrinsic temporal and voltage resolutions of < 500 fs and < 1 mV. In actual experiments, the connection-limited time resolution was 55 ps or 16 ps, depending on whether the detector was placed in room or cryogenic environment. The measured response of the tunnel junction was found to be consistent with the RSJ model.

Direct electro-optic sampling of transmission-line signals propagating on a GaAs substrate

We report a new picosecond electro-optic sampling probe suitable for noncontact electronic characterisation of high-speed monolithic GaAs integrated circuits.

Picosecond electro-optic sampling system

We report the construction of a sensitive electro-optic sampling system for the measurement of ultrafast electrical transients. This system has a temporal resolution of lessthan 4 ps (over 100- GHz bandwidth), better than 50-μV sensitivity and potential for a temporal resolution reaching the single picosecond. Demonstrated applications are ultrafast photodetector response characterization and time resolved photoconductivity.