Thorlabs offers a wide selection of power and energy meter consoles and interfaces for operating our power and energy sensors. Key specifications of all of our power meter consoles and interfaces are presented below to help you decide which device is best for your application. We also offer self-contained wireless power meters and compact USB power meters.

When used with our C-series sensors, Thorlabs' power meter consoles and interfaces recognize the type of connected sensor and measure the current or voltage as appropriate. Our C-series sensors have responsivity calibration data stored in their connectors. The console will read out the responsivity value for the user-entered wavelength and calculate a power or energy reading.

• Photodiode sensors deliver a current that depends on the input optical power and the wavelength. The current is fed into a transimpedance amplifier, which outputs a voltage proportional to the input current. The photodiode's responsivity is wavelength dependent, so the correct wavelength must be entered into the console for an accurate power reading. The console reads out the responsivity for this wavelength from the connected sensor and calculates the optical power from the measured photocurrent.
• Thermal sensors deliver a voltage proportional to the input optical power. Based on the measured sensor output voltage and the sensor's responsivity, the console will calculate the incident optical power.
• Energy sensors are based on the pyroelectric effect. They deliver a voltage peak proportional to the pulse energy. If an energy sensor is recognized, the console will use a peak voltage detector and the pulse energy will be calculated from the sensor's responsivity.

The consoles and interfaces are also capable of providing a readout of the current or voltage delivered by the sensor. Select models also feature an analog output.

Consoles

Item #	PM100A	PM100D	PM400	PM320E
(Click Photo to Enlarge)
Key Features	Analog Power Measurements	Digital Power and Energy Measurements	Digital Power and Energy Measurements, Touchscreen Control	Dual Channel
Compatible Sensors	Photodiode and Thermal Power	Photodiode and Thermal Power; Pyroelectric
Housing Dimensions (H x W x D)	7.24" x 4.29" x 1.61" (184 mm x 109 mm x 41 mm)	7.09" x 4.13" x 1.50" (180 mm x 105 mm x 38 mm)	5.35" x 3.78" x 1.16" (136.0 mm x 96.0 mm x 29.5 mm)	4.8" x 8.7" x 12.8" (122 mm x 220 mm x 325 mm)
Channels	1			2
External Temperature Sensor Input (Sensor not Included)	-	-	Instantaneous Readout and Record Temperature Over Time	-
External Humidity Sensor Input (Sensor not Included)	-	-	Instantaneous Readout and Record Humidity Over Time	-
GPIO Ports	-		4, Programmable	-
Source Spectral Correction	-	-		-
Attenuation Correction	-	-		-
External Trigger Input	-	-	-
Display
Type	Mechanical Needle and LCD Display with Digital Readout	320 x 240 Pixel Backlit Graphical LCD Display	Protected Capacitive Touchscreen with Color Display	240 x 128 Pixels Graphical LCD Display
Dimensions	Digital: 1.9" x 0.5" (48.2 mm x 13.2 mm) Analog: 3.54" x 1.65" (90.0 mm x 42.0 mm)	3.17" x 2.36" (81.4 mm x 61.0 mm)	3.7" x 2.1" (95 mm x 54 mm)	3.7" x 2.4" (94.0 mm x 61.0 mm)
Refresh Rate	20 Hz		10 Hz (Numerical) 25 Hz (Analog Simulation)	20 Hz
Measurement Viewsa
Numerical
Mechanical Analog Needle		-	-	-
Simulated Analog Needle	-
Bar Graph	-
Trend Graph	-
Histogram	-		-
Statistics
Memory
Type	-	SD Card	NAND Flash	-
Size	-	2 GB	4 GB	-
Power
Battery	LiPo 3.7 V 1300 mAh		LiPo 3.7 V 2600 mAh	-
External	5 VDC via USB or Included AC Adapter		5 VDC via USB	Selectable Line Voltage: 100 V, 115 V, 230 V (±10%)

• These are the measurement views built into the unit. All of our power meter consoles except the PM320E can be controlled using the Optical Power Monitor software package. The PM320E has its own software package.

Interfaces

Item #	PM101	PM102	PM101A	PM102A	PM101R	PM101U	PM102U	PM100USB
(Click Photo to Enlarge)
Key Features	USB, RS232, UART, and Analog Operation		USB and Analog SMA Operation		USB and RS232 Operation	USB Operation		USB Operation
Compatible Sensors	PM101 Series: Photodiode and Thermal Power PM102 Series: Thermal Power and Thermal Position & Power							Photodiode and Thermal Power; Pyroelectric
Housing Dimensions (H x W x D)	3.80" x 2.25" x 1.00" (96.5 x 57.2 x 25.4 mm)		3.94" x 2.25" x 1.00" (100.0 x 57.2 x 25.4 mm)		3.78" x 2.25" x 1.00" (95.9 x 57.2 x 25.4 mm)	3.68" x 2.25" x 1.00" (93.6 x 57.2 x 25.4 mm)		3.67" x 2.38 " x 1.13" (93.1 x 60.4 x 28.7 mm)
Channels	1
External Temperature Sensor Input (Sensor Not Included)	NTC Thermistor		-
External Humidity Sensor Input (Sensor not Included)	-
GPIO Ports	-
Source Spectral Correction	-
Attenuation Correction	-
External Trigger Input	-
Display
Type	No Built-In Display; Controlled via GUI for PC
Refresh Rate	Up to 1000 Hza							Up to 300 Hza
Measurement Viewsb
Numerical	Requires PCb
Mechanical Analog Needle	-
Simulated Analog Needle	Requires PCb
Bar Graph	Requires PCb
Trend Graph	Requires PCb
Histogram	Requires PCb
Statistics	Requires PCb
Memory
Type	Internal Non-Volatile Memory for All Settings							-
Size	-
Power
Battery	-
External	5 VDC via USB or 5 to 36 VDC via DA-15		5 VDC via USB

• Dependent on PC Settings
• These power meter interfaces do not have a built-in monitor, so all data must be displayed through a PC running the Optical Power Meter Software.

Insights into Best Lab Practices

Scroll down to read about things to consider when building integrating spheres into setups and analyzing data results.

• Ultraviolet and Blue Fluorescence Emitted by Integrating Spheres
• Sample Substitution Errors

Click here for more insights into lab practices and equipment.

Ultraviolet and Blue Fluorescence Emitted by Integrating Spheres

Click to Enlarge
Figure 1: Typical yields at each wavelength are around four orders of magnitude lower than the excitation wavelength. [4]

The spectral fluorescence yield relates the intensity of the fluorescence emitted within the integrating sphere with the intensity of the excitation wavelength. The yield is calculated by dividing the wavelength-dependent, total fluorescence excited over the entire interior surface of the sphere by the intensity of the light excitation.

Data were kindly provided by Dr. Ping-Shine Shaw, Physics Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.

A material of choice for coating the light-diffusing cavities of integrating spheres is polytetrafluoroethylene (PTFE). This material, which is white in appearance, is favored for reasons including its high, flat reflectance over a wide range of wavelengths (see the Specs tab for details) and chemical inertness.

However, it should be noted that integrating spheres coated with both PTFE and barium sulfate, which is an alternative coating with lower reflectance, emit low levels of ultraviolet (UV) and blue fluorescence when irradiated by UV light. [1-3]

Hydrocarbons in the PTFE Fluoresce
It is not the PTFE that fluoresces. The sources of the UV and blue fluorescence are hydrocarbons in the PTFE. Low levels of hydrocarbon impurities are present in the raw coating material, and pollution sources deposit additional hydrocarbon contaminants in the PTFE material of the integrating sphere during its use and storage. [1]

Fluorescence Wavelength Bands and Strength
Researchers at the National Institute of Standards and Technology (NIST) have investigated the fluorescence excited by illuminating PTFE-coated integrating spheres. The total fluorescence output by the integrating sphere was measured with respect to fluorescence wavelength and excitation wavelength. The maximum fluorescence was approximately four orders of magnitude lower than the intensity of the exciting radiation.

The UV and blue fluorescence from PTFE is primarily excited by incident wavelengths in a 200 nm to 300 nm absorption band. The fluorescence is emitted in the 250 nm to 400 nm wavelength range, as shown by Figure 1. These data indicate that increasing the excitation wavelength decreases the fluorescence emitted at lower wavelengths and changes the shape of the fluorescence spectrum.

As the levels of hydrocarbon contaminants in the PFTE increase, fluorescence increases. A related effect is a decrease of the light output by the integrating sphere over the absorption band wavelengths, due to more light from this spectral region being absorbed. [1, 3]

Impact on Applications
The UV and blue fluorescence from the PTFE has negligible effect on many applications, since the intensity of the fluorescence is low and primarily excited by incident wavelengths <300 nm. Applications sensitive to this fluorescence include long-term measurements of UV radiation throughput, UV source calibration, establishing UV reflectance standards, and performing some UV remote sensing tasks. [1]

Minimizing Fluorescence Effects
Minimizing and stabilizing the fluorescence levels requires isolating the integrating sphere from all sources of hydrocarbons, including gasoline- and diesel-burning engine exhaust and organic solvents, such as naphthalene and toluene. It should be noted that, while hydrocarbon contamination can be minimized and reduced, it cannot be eliminated. [1]

Since the history of each integrating sphere's exposure to hydrocarbon contaminants is unique, it is not possible to predict the response of a particular sphere to incident radiation. When an application is negatively impacted by the fluorescence, calibration of the integrating sphere is recommended. A calibration procedure described in [4] requires a light source with a well-known spectrum that extends across the wavelength region of interest, such as a deuterium lamp or synchrotron radiation, a monochromator, a detector, and the integrating sphere.

References
[1] Ping-Shine Shaw, Zhigang Li, Uwe Arp, and Keith R. Lykke, "Ultraviolet characterization of integrating spheres," Appl.Opt. 46, 5119-5128 (2007).
[2] Jan Valenta, "Photoluminescence of the integrating sphere walls, its influence on the absolute quantum yield measurements and correction methods," AIP Advances 8, 102123 (2018).
[3] Robert D. Saunders and William R. Ott, "Spectral irradiance measurements: effect of UV-produced fluorescence in integrating spheres," Appl. Opt. 15, 827-828 (1976).
[4] Ping-Shine Shaw, Uwe Arp, and Keith R. Lykke, "Measurement of the ultraviolet-induced fluorescence yield from integrating spheres," Metrologia 46, S191 - S196 (2009).

Date of Last Edit: Dec. 4, 2019

Sample Substitution Errors

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Click to Enlarge
Figure 2: Measuring diffuse sample transmittance and reflectance as shown above can result in a distorted sample spectrum due to sample substitution error. The problem is that the reflectivity over the sample area is different during the reference and sample measurements.

Click to Enlarge
Figure 3: The above configuration is not susceptible to sample substitution error, since the interior of the sphere is the same for reference and sample measurements. During the reference measurement the light travels along (R), and no light is incident along (S). The opposite is true when a sample measurement is made.

Absolute transmittance and absolute diffuse reflectance spectra of optical samples can be found using integrating spheres. These spectra are found by performing spectral measurements of both the sample of interest and a reference.

Measurement of a reference is needed since this provides the spectrum of the illuminating light source. Obtaining the reference scan allows the spectrum of the light source to be subtracted from the sample measurement.

The light source reference measurement is made with no sample in place for transmittance data and with a highly reflective white standard reference sample in place for reflectance measurements.

Sample substitution errors incurred while acquiring the sample and reference measurement sets can negatively effect the accuracy of the corrected sample spectrum, unless the chosen experimental technique is immune to these errors.

Conditions Leading to Sample Substitution Errors
An integrating sphere's optical performance depends on the reflectance at each point on its entire inner surface. Often, a section of the sphere's inner wall is replaced by the sample when its transmittance and diffuse reflectance spectra are measured (Figure 2). However, modifying a section of the inner wall alters the performance of the integrating sphere.

Sample substitution errors are a concern when the measurement procedure involves physically changing one sample installed within the sphere for another. For example, when measuring diffuse reflectance (Figure 2, bottom), a first measurement might be made with the standard reference sample mounted inside the sphere. Next, this sample would be removed and replaced by the sample of interest, and a second measurement would be acquired. Both data sets would then be used to calculate the corrected absolute diffuse reflectance spectrum of the sample. 

This procedure would result in a distorted absolute sample spectrum. Since the sample of interest and the standard reference have different absorption and scattering properties, exchanging them alters the reflectivity of the integrating sphere over the samples' surface areas. Due to the average reflectivity of the integrating sphere being different for the two measurements, they are not perfectly compatible.

Solution Option: Install Sample and Reference Together
One experimental technique that avoids sample substitution errors acquires measurement data when both sample and reference are installed inside the integrating sphere at the same time. This approach requires an integrating sphere large enough to accomodate the two, as additional ports. 

The light source is located external to the integrating sphere, and measurements of the sample and standard reference are acquired sequentially. The specular reflection from the sample, or the transmitted beam, is often routed out of the sphere, so that only the diffuse light is detected. Since the inner surface of the sphere is identical for both measurements, sample substitution errors are not a concern.

Alternate Solution Option: Make Measurements from Sample and Reference Ports
If it is not possible to install both sample and standard references in the integrating sphere at the same time, it is necessary to exchange the installed sample. If this must be done, sample substitution errors can be removed by following the procedure detailed in [1].

This procedure requires a total of four measurements. When the standard sample is installed, measurements are made from two different ports. One has a field of view that includes the sample and the other does not. The sample of interest is then subsituted in and the measurements are repeated. Performing the calculations described in [1] using these measurements removes the sample substitution errors.

References
[1] Luka Vidovic and Boris Majaron, "Elimination of single-beam substitution error in diffuse reflectance measurements using an integrating sphere," J. Biomed.Opt. 19, 027006 (2014).

Date of Last Edit: Dec. 4, 2019

Click to Enlarge
The PM160 wireless power meter, shown here with an iPad mini (not included), can be remotely operated using Apple mobile devices.

This tab outlines the full selection of Thorlabs' power and energy sensors. Refer to the lower right table for power meter console and interface compatibility information.

In addition to the power and energy sensors listed below, Thorlabs also offers all-in-one, wireless, handheld power meters and compact USB power meter interfaces that contain either a photodiode or a thermal sensor, as well as power meter bundles that include a console, sensor head, and post mounting accessories.

Thorlabs offers four types of sensors:

• Photodiode Sensors: These sensors are designed for power measurements of monochromatic or near-monochromatic sources, as they have a wavelength dependent responsivity. These sensors deliver a current that depends on the input optical power and the wavelength. The current is fed into a transimpedance amplifier, which outputs a voltage proportional to the input current.
• Thermal Sensors: Constructed from material with a relatively flat response function across a wide range of wavelengths, these thermopile sensors are suitable for power measurements of broadband sources such as LEDs and SLDs. Thermal sensors deliver a voltage proportional to the input optical power.
• Thermal Position & Power Sensors: These sensors incorporate four thermopiles arranged as quadrants of a square. By comparing the voltage output from each quadrant, the unit calculates the beam's position.
• Pyroelectric Energy Sensors: Our pyroelectric sensors produce an output voltage through the pyroelectric effect and are suitable for measuring pulsed sources, with a repetition rate limited by the time constant of the detector. These sensors will output a peak voltage proportional to the incident pulse energy.

Console Compatibility
Console Item #	PM100A	PM100D	PM400	PM320E	PM101 Series	PM102 Series	PM100USB
Photodiode Power						-
Thermal Power
Thermal Position	-	-		-	-		-
Pyroelectric Energy	-				-	-

Power and Energy Sensor Selection Guide

There are two options for comparing the specifications of our Power and Energy Sensors. The expandable table below sorts our sensors by type (e.g., photodiode, thermal, or pyroelectric) and provides key specifications.

Alternatively, the selection guide graphic further below arranges our entire selection of photodiode and thermal power sensors by wavelength (left) or optical power range (right). Each box contains the item # and specified range of the sensor. These graphs allow for easy identification of the sensor heads available for a specific wavelength or power range.

Sensor Type	Applications	Item #	Wavelength	Energy or Power Range	Detector Type	Aperture	Response Time
Standard Sensors	General Purpose Power Measurements	S120VC	200 - 1100 nm	50 nW - 50 mW	Si	Ø9.5 mm	<1 µsa
		S120C	400 - 1100 nm	50 nW - 50 mW		Ø9.5 mm
		S121C	400 - 1100 nm	500 nW - 500 mW		Ø9.5 mm
		S122C	700 - 1800 nm	50 nW - 40 mW	Ge	Ø9.5 mm
Slim Sensors	Power Measurements in Tight Spaces	S130VC	200 - 1100 nm	Dual Range: 5 nW - 5 mW or 50 nW - 50 mW	Si Slim	Ø9.5 mm
		S130C	400 - 1100 nm	Dual Range: 500 pW - 5 mW or 100 µW - 500 mW		Ø9.5 mm
		S132C	700 - 1800 nm	Dual Range: 5 nW - 5 mW or 100 µW - 500 mW	Gi Slim	Ø9.5 mm
Microscope Slide Sensor	Measure Power at the Sample Plane of a Microscope	S170C	350 - 1100 nm	10 nW - 150 mW	Si Large Area	18 mm x 18 mm
Integrating Sphere Sensors	Power Measurements for High Powers and Divergent Beams	S140C	350 - 1100 nm	1 µW - 500 mW	Si Integrating	Ø5 mm
		S142C	350 - 1100 nm	5 µW - 5 W		Ø12 mm
		S144C	800 - 1700 nm	100 nW - 500 mW	InGaAs Integrating	Ø5 mm
		S145C	800 - 1700 nm	1 µW - 3 W		Ø12 mm
		S146C	900 - 1650 nm	10 µW - 20 W		Ø12 mm
		S148C	1200 - 2500 nm	1 µW - 1 W		Ø5 mm
		S180C	2900 - 5500 nm	1 µW - 3 W	MCT (HgCdTe)	Ø7 mm
Fiber Sensors	Fiber Power Measurements and Field Applications	S150C	350 - 1100 nm	100 pW - 5 mW	Si Fiber	Ø5 mm
		S151C	400 - 1100 nm	1 nW - 20 mW		Ø5 mm
		S154C	800 - 1700 nm	100 pW - 3 mW	InGaAs Fiber	Ø5 mm
		S155C	800 - 1700 nm	1 nW - 20 mW		Ø5 mm

Sensor Type	Applications	Item #	Wavelength	Energy or Power Range	Detector Type	Aperture	Response Timeb
High Resolution	Broadband Measurements of Optical Powers ≤5 W with 1 µW or 5 µW Resolution	S401C	190 nm - 20 µm	10 µW - 1 W (3 Wc)	Thermal Surface Absorber with Background Compensation	Ø10 mm	1.1 s
		S405C	190 nm - 20 µm	100 µW - 5 W	Thermal Surface Absorber	Ø10 mm	1.1 s
Max Power: 10 W	General Broadband Power Measurements of Low and Medium Power Light Sources	S415C	190 nm - 20 µm	2 mW - 10 W (20 Wc)		Ø15 mm	0.6 s
		S425C	190 nm - 20 µm	2 mW - 10 W (20 Wc)		Ø25.4 mm	0.6 s
Max Power: 40 W to 200 W		S350C	190 nm - 1.1 µm, 10.6 µm	10 mW - 40 W (60 Wc)		Ø40 mm	9 s (1 s from 0 to 90%)
		S425C-L	190 nm - 20 µm	2 mW - 50 W (75 Wc)		Ø25.4 mm	0.6 s
		S322C	250 nm - 11 µm	100 mW - 200 W (250 Wc)		Ø25 mm	5 s (1 s from 0 to 90%)
High Max Power Density	Optical Power Measurements of Nd:YAG and Other Pulsed Laser Sources	S370C	400 nm - 5200 nm	10 mW - 10 W (15 Wc)	Thermal Volume Absorber	Ø25 mm	45 s (3 s from 0 to 90%)
		S470C	250 nm - 10.6 µm	100 µW - 5 W		Ø15 mm	6.5 s (<2 s from 0 to 90%)
Microscope Slide	Measure Power at the Sample Plane of a Microscope	S175C	300 nm - 10.6 µm	100 µW - 2 W	Thermal Surface Absorber	18 mm x 18 mm	3 s (<2 s from 0 to 90%)

Sensor Type	Applications	Item #	Wavelength	Power Range	Detector Type	Aperture	Response Timeb
High Resolution	Precise Beam Position and Power Measurements of Low and Medium Power Lasers	S440C	190 nm - 20 µm	0.5 mW - 5 W	Thermal Absorber, Four Quadrants	17 x 17 mm	<1.1 s
High Power		S442C	190 nm - 20 µm	10 mW - 50 W	Thermal Absorber, Four Quadrants	Ø17.5 mm	<0.6 s

Sensor Type	Applications	Item #	Wavelength	Energy or Power Range	Detector Type	Aperture	Response Time
Standard Energy Sensors	General Purpose Energy Meter	ES111C	185 nm - 25.0 µm	10 µJ - 150 mJ	Pyroelectric	Ø11 mm	N/Ad
		ES120C	185 nm - 25.0 µm	100 µJ - 500 mJ		Ø20 mm
		ES145C	185 nm - 25.0 µm	500 µJ - 2 J		Ø45 mm
High Energy Sensors	High Energy Measurements for High Peak Energy Lasers: Excimer, CO2-TEA, and Nd:YAG	ES220C	185 nm - 25.0 µm	500 µJ - 3 J	Pyroelectric Ceramic Coating	Ø20 mm
		ES245C	185 nm - 25.0 µm	1 mJ - 15 J		Ø45 mm

• The response time of the photodiode sensor. The actual response time of a power meter using these sensors will be limited by the update rate of your power meter console.
• Typical natural response time (0 - 95%). Our power consoles can provide estimated measurements of optical power on an accelerated time scale (typically <1 s) when the natual response time is approximately 1 s or greater. As the natural response times of the S415C, S425C, and S425C-L are fast, these do not benefit from accelerated measurements and this function cannot be enabled. For more information, see the Operation tab here.
• With intermittent use: maximum exposure time of 20 minutes for the S401C, otherwise maximum exposure time is 2 minutes.
• All pyroelectric sensors have a 20 ms thermal time constant, τ. This value indicates how long it takes the sensor to recover from a single pulse. To detect the correct energy levels, pulses must be shorter than 0.1τ and the repetition rate of your source must be well below 1/τ.

Sensor Options
(Arranged by Wavelength Range)

Sensor Options
(Arranged by Power Range)