A sensitive calorimeter using an isothermal temperature control technique was developed for an accurate measurement of microwatt-level laser power in the visible and infrared spectral region. The standard deviation of the measured value on 1-mW-1-μW laser power is 0.06–2 percent corresponding to the level. The systematic error is evaluated to be within ±0.23 percent for the 10 μW level.

https://ieeexplore.ieee.org/iel5/19/6312653/06312754.pdf

Highly sensitive calorimeter for microwatt-level laser power measurements

We developed a calorimeter for determining absolute terahertz (THz) power. The calorimeter is based on a DC substitution method using an isothermal temperature-control technique. A neutral-density optical filter glass was used as a volume absorber, and its THz absorption was evaluated by a time-domain spectrometer. Highly sensitive measurement of the absolute THz power was experimentally achieved in the range from the submicrowatt to microwatt level at room temperature. Power measurement of a continuous-wave THz source using a photomixer was demonstrated. This calorimeter is expected to demonstrate the traceability of THz power at a submicrowatt level.

Calorimetric measurement of absolute terahertz power at the sub-microwatt level.

A review of the state of the art of picosecond time-domain waveform measurements is presented which includes measurements in both the electrical and optical regions of the electromagnetic spectrum. This review is the latest edition of a series of reviews on high-speed pulse measurements compiled by the author commencing in 1967 [1]; specifically this review updates the 1978 review, [2]. The significance of the IEEE Pulse Standards 181 and 194 (or the identical IEC Standards 469-1 and 469-2) are discussed briefly. The classification of time-domain measurements from the 1978 review is summarized and augmented with basic instrumentation block diagrams. The advances in the present-day capabilities from those in 1978 are presented via temporal resolution state-of-the-art charts using the 1978 format; however, the only entries in the charts are those that have changed since 1978. Also, presented are some opinions as to the future directions of electrical and optical picosecond domain measurements. Fifty-six references are cited.

Picosecond-Domain Waveform Measurement: Status and Future Directions

A system for measuring laser pulse durations in the range of ten nanoseconds to one femtosecond to an accuracy of one femtosecond, includes a primary pulse sampler, a ten component beam splitter array, optical delay lines whose settings are microprocessor controlled, a ten section interaction chamber with ten sets of ion detectors and a pulse envelope and pulse energy display monitors. The system has applications in chemistry, calibration of fast timing circuits and in the development of short pulse lasers.

Femtosecond laser pulse measuring system

A terminator system particularly suited for beams of high intensity electromagnetic radiation such as from a laser includes an enclosure having a hole therein and a black mirror mounted in the enclosure. The black mirror has a specularly reflecting surface opposite the hole and is oriented at an angle such that the beam impinging on the hole would be impinging on the specularly reflecting surface and would not be reflected directly back out the hole. The black mirror is constructed of a material that absorbs energy at the wavelength of the incident beam. In another preferred embodiment, there are a plurality of black mirrors for performing a succession of reflections, so that the beam power is reduced significantly at each reflection.

Blackhole laser beam terminator

A microprocessor-based calibration system for a CW laser power meter has been developed. The system consists of an isothermal calorimeter with a thermopile unit, an electrical, and an optical subsystem. Temperature control of the thermopile unit is achieved through a digital technique. The calibration of a power meter is performed using the effective efficiency of the unit as measured by a calorimeter. From error analyses, an overall accuracy has been obtained as ±1 percent in root mean square for a power level of 1 ~ 200 mW.

Automatic Calibration System for a Laser Power Meter

A laser-light absorber including a metal body and a flame-sprayed film essentially consisting of metal oxide applied on the metal body. The laser-absorbing properties of a laser-shield for laser welding, cutting, hardening machines, and the like are improved by applying the flame-sprayed film on the metal body.

Laser-light absorber and method for absorbing laser light

This paper deals with measurements of picosecond laser pulse parameters such as temporal and spatial profile, and power. Pulseshape measurements were conducted by using the combined streak camera and optical multichannel analyzer system. The precision of measurements are discussed.

Measurements of picosecond laser pulses from mode-locked Nd:YAG laser

In this paper we describe results of the international intercomparison of He-Ne and Ar-ion laser power measurements. The intercomparison measurements were of He-Ne laser power of 3 mW at the wavelength of 633 nm and Ar-ion laser power of 200 mW at 488 nm and 515 nm. The participating laboratories coincided within deviation from the average of 0.6 percent at 633 nm, 0.8 percent at 488 nm, and 0.9 percent at 515 nm.

Michiyuki Endo

Papers

Automatic Calibration System for a Laser Power Meter

Laser-light absorber and method for absorbing laser light

Measurements of picosecond laser pulses from mode-locked Nd:YAG laser

International Intercomparison of Laser Power Measurements in the Visible Region