JPH0622188Y2 - Optical power meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to an optical power meter, and more particularly to an optical power meter for measuring the power of large output pulsed light.

<Prior Art> Conventionally, a photoelectric conversion method of a semiconductor such as a photodiode and a photothermal conversion method (that is, a calorimeter method) are often used in the measurement of optical power.

This prior art will be described below with reference to the drawings.

FIG. 3 is a diagram for explaining the conventional technique.
In the figure, a diagram for explaining the principle of a photodiode as a typical example of a photoelectric conversion system is shown.

In FIG. 3, the measurement light α _in passes through the light receiving surface (P layer) 1.
Is incident, an electron-hole pair 4 is generated by photoexcitation in a PN junction (depletion layer) 3 formed by joining the P layer 1 and the N substrate 2, and this is converted into a photocurrent L _i proportional to the optical power. Flowing on the circuit. The photoelectric conversion method measures the optical power of the measurement light α _in by measuring this current value.

FIG. 4 is a diagram for explaining the conventional technique.
In the figure, a diagram for explaining the principle of a typical example of the calorimeter method is shown.

In FIG. 4, in the calorimeter method, the measurement light α _in entering from the entrance 5a is received and absorbed inside the heat insulating jacket 5 for reducing the influence of ambient temperature fluctuations, and is converted into thermal energy, for example. A light absorber 6 which is formed of a good heat conductor such as aluminum into a cylindrical shape or a disk shape and whose light-receiving surface is coated with a material having a high light absorption rate is installed.
The measurement light α _in is converted into heat energy by the light absorber 6, and the heat energy at that time is converted into heat energy and a reference temperature body (having a sufficiently large heat capacity as compared with the light absorber 6 and a temperature of a short time). The optical power of the measuring light α _in is measured by detecting the temperature difference with the temperature difference detector 7 and the output (E _out ).

<Problems to be Solved by the Invention> These conventional techniques have the following problems.

: The photoelectric conversion method of FIG. 3 has high measurement sensitivity and responds at high speed, so it is suitable for measuring minute optical power and power waveform of high-speed optical pulse, but when the optical power increases, saturation of photocurrent and device Is destroyed, and the limit is about 50 mW.

: In the calorimeter method of FIG. 4, the absolute power can be measured and the heat resistance of the light absorber 6 is improved to be several W.
Although it has the advantage that it can sufficiently support the measurement of large output light power of several KW or more, it has a low photothermal conversion response of the light absorber and is on the order of a few seconds to a minute, so it is an average for high-speed light pulses, etc. Only power can be measured.

The present invention has been made in view of the above problems of the prior art, and an object thereof is to provide an optical power meter capable of measuring the power waveform of a high-speed high-speed optical pulse. is there.

<Means for Solving the Problems> In order to achieve the above object, the optical power meter of the present invention has a heat-resistant structure that absorbs incident measuring light and converts the optical power at that time into heat. A good light absorber is installed, and the heat energy when the measuring light is converted into heat by the light absorber is measured by the temperature difference detection element as the temperature difference between the reference temperature body and the light absorber. A high-speed response light receiving element is arranged at a position where a part of the reflected light passes, and the optical pulse power waveform of the measurement light is measured.

<Example> An example will be described with reference to the drawings.

In the following drawings, the same parts as those in FIG. 4 are designated by the same reference numerals and the description thereof will be omitted.

FIG. 1 is a schematic configuration diagram of an optical power meter showing a specific embodiment of the present invention.

In FIG. 1, reference numeral 9 denotes a light absorber 6 having a high heat resistance that absorbs incident measurement light and converts the optical power at that time into heat, which is a small part of the reflected light β.
Where light passes, in other words, the measurement light α _in is absorbed by the light absorber 6
High-speed response light-receiving element for detecting optical power, such as a PIN photodiode, provided at a position where the irregular reflection light β generated when the light-receiving surface is detected (hereinafter referred to as “optical power detection element”) Is. By the way, when the PIN photodiode is used for the optical power detection element 9, the measurement limit of the PIN photodiode is several tens mW, while the light absorber 6 is several W to several KW.
It is possible to sufficiently deal with the measurement of the above large output light power. Therefore, it is useless to simply arrange them in parallel, but with the configuration shown in FIG. 1, the reflected light β at the light absorber 6 is less than a few% of the measurement light, and a part of it is received. Therefore, even if the optical power of the measuring light α _in is large, the light receiving power of the optical power detecting element 9 is reduced to a measurable level, so that a sufficient effect can be exhibited. Becomes As a result, it becomes possible to measure and output the power waveform of the high-speed optical pulse having a large optical power of the measurement light.

FIG. 2 is an optical power time chart used for the explanation of FIG.

Further description will be given below with reference to FIG.

1 and 2, in FIG. 2 (i) (example of high-output high-speed pulse measurement light data, at this time, l = 1 to 100 W, τ
= Msec to nsec, pulse waveform in the case of D = several tens) When high-speed, high-speed optical pulse measurement light enters the light absorber 6, the thermal time constant of the light absorber 6 is from several seconds to several tens of seconds. Since it is large, it does not follow each optical pulse power.
(ii) A temperature rise corresponding to the average power as shown in (Example of temperature rise of light absorber, where T corresponds to average power). Therefore, if this temperature rise is measured by the temperature difference detecting element 8, the average power of the light pulse can be known. on the other hand,
The light incident on the optical power detection element 9 is a part of the reflected light β from the light absorber 6, and this optical power is reduced to a level measurable by the optical power detection element 9, and the measurement light α
_It has an optical pulse power waveform with almost the same profile as in. Since the optical power detection element 9 responds at high speed,
If the photocurrent waveform is measured, this power waveform (of the high-speed optical pulse with a large optical power of the measurement light) is shown in FIG. 2 (iii).
(Example of photodiode current waveform, where η = 1 mW
Pulse waveform in the case of ˜1 μW). In this way, the average power of the high-speed and high-speed pulsed light (as described above, the thermal energy when the measurement light is converted into heat by the light absorber is used as the temperature difference between the reference temperature body and the temperature difference detection element) Since the measurement) and the power waveform can be measured simultaneously, the absolute value of the peak power of the pulse can also be obtained from these two measurement results.

<Effects of the Invention> Since the present invention is configured as described above, it has the following effects.

: Since the optical power is measured simultaneously by the calorimeter and the high speed light receiving element such as the photodiode, the average power and the power waveform of the large output pulsed light can be measured at the same time.

: Since the light detected by the optical power detecting element uses a part of the reflected light of the light absorber of the calorimeter part, it can be greatly reduced to a level that can be measured by the optical power detecting element even when measuring a large output light.

: In order to measure the optical power at the sensor with a high-speed photodetector such as a photodiode, it is common to use an optical power attenuator to reduce the received light power. In this case, the optical power attenuator is used. Since most of the optical power is reflected, it is extremely dangerous in terms of work, but with the configuration of the present invention, such a situation does not occur.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an optical power meter showing a concrete embodiment of the present invention, FIG. 2 is an optical power time chart used for the explanation of FIG. 1, and FIGS. 3 and 4 are explanations of conventional techniques. FIG. 5 ... Adiabatic jacket, 6 ... Light absorber, 7 ... Reference temperature body, 8 ... Temperature difference detecting element, 9 ... Optical power detecting element.

Claims (1)

[Scope of utility model registration request] 1. A heat-absorbing light absorber that absorbs incident measuring light and exchanges the optical power at that time into heat is installed inside the heat insulating jacket, and the measuring light is converted into heat by the light absorbing body. While measuring the thermal energy as a temperature difference between the reference temperature body and the temperature difference detection element, the high-speed response light receiving element is arranged at a position where a small part of the reflected light in the light absorber passes. An optical power meter characterized by measuring an optical pulse power waveform of measuring light.