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ProPhotonix
Prophotonix
Questions?

FAQs

Laser FAQs

What is MQW structure?
In MQW (multi quantum well) structure, the active layer of the laser diode is a laminated structure comprising quantum well layers and barrier layers with a thickness of several nm. By regulating the composition of the quantum well layers that constitute the light emitting area, and using a crystal with a smaller lattice constant than the substrate, tensile stain is introduced into the quantum well layers. The band structure varies due to this strain, resulting in a lower threshold current and higher slope efficiency.


What is the coherence length?
Most laser diode manufacturers do not measure this parameter. Typically, laser diodes are index-guided devices with 3x1µm emitting dimensions. Coherence length is approximately several centimetres.


Is it single mode / single frequency?
Most laser diodes have a single mode structure with typical emitting dimensions of 3x1µm. However, Fabry Perot cavity laser diodes will mode hop, are sensitive to back reflections and may have regions in the power / current curve that are multi mode. So, yes, they are single mode / single frequency, but they will mode hop and may have multi mode operating regions.


What is the maximum modulation bandwidth?
Typically 5.6mm and 9mm packaged laser diodes have a modulation bandwidth in excess of 500 MHz


Can the laser be pulsed?
Yes, but the maximum CW power should be observed


Can the laser be operated below -10°C?
Performance below -10°C has not been tested and is not recommended or guaranteed. It is likely that the laser will work but lifetime, optical and electrical performance will be reduced. Also the package may not remain hermetically sealed.


Can laser diodes be wavelength selected?
Yes they can, typically a ±3nm selection, subject to prior approval. A selection surcharge will be applied, details of which are available on request. Wavelength selection of devices in stock is possible at no surcharge. However, future availability of a particular wavelength cannot be guaranteed.


Do you have laser diodes at wavelength X, power Y?
If the requested wavelength and / or power is not on the website, then please contact us to discuss your requirements.


Do you offer DFB or DBR laser diodes??
We stock 1310nm and 1550nm DFB laser diodes.


Do you offer telecomms diodes?
Typically telecomms diodes are 1300nm, 1550nm or 980nm and they may be DFB or DBR structures.We stock a range of 1310nm, 1550nm Fabry Perot and DFB laser diodes for telecommunications.


LED FAQs

Does ProPhotonix make LEDs?
ProPhotonix sources LEDs, mostly unpackaged LED chips, from reputable, established companies that make the LED wafers themselves.  Sourcing the LEDs is a core competency developed from more than a decade of experience. The LEDs are selected based on wavelength, power, and price according to the specification of the product or goals and constraints of the custom design.  We place these LEDs on a thermally efficient PCB substrate of our design, wire bond to complete the circuit, and assemble this “Light Engine” into a higher level assembly that can include optics, mechanics, thermal management features, as well as control electronics.  By starting with the smallest, most basic building block, the LED chip itself, we have the most control possible for every aspect of the design and performance.


What is Chip-on-Board LED packaging?
Chip-on-Board (COB) LED packaging refers to placing the LED die directly on a PCB substrate where it is fixed by silvered epoxy or solder. The intended circuit is then completed with wire bonds between the LED chips and the PCB. Generally, an encapsulation, hard of soft, is used to protect the wire bonds and LEDs.  As the LED chip is the smallest light building block available, the light engine itself can be a highly customized, application specific device with many LEDs with almost any spacing or array dimension.  Multiple colors and driving circuits can be designed.  Optics can be mounted directly to the PCB. The electronics if desired can be on or off the PCB (or light).  The LED chips ranging in size generally from ~300 microns to 1-mm per side can be considered Lambertian emitters and have no integrated optics like common through-hole or surface mount devices.  This allows the optical performance to be customized for the application starting with the most basic element.  The chips are directly mounted to PCB substrate so the heat is removed from the LED more efficiently than through several intermediate junctions in a surface mount LED or through the leads in a through-hole LED package.  In short Chip-on-Board is ideal for the highest performance or highly constrained applications.


Can you modify your standard product or create a new design for my needs?
Yes. Please tell us about your project and if it is something physically possible with LEDs and commercially viable, we can do it.


What colors or wavelengths are available?
LEDs are available in many wavelengths from 250 nm in the UV to several microns in the IR.  In some parts of the visible spectrum an LED with a peak wavelength may be available every 5-10nm.  However in some parts of the spectrum there are no LEDs available due to technology limitations.    


Can you put multiple wavelengths in a single light?
Yes.  We do so commonly for custom OEM projects.  Please contact us for more information.


Can I replicate the spectrum of a fluorescent, halogen or other black body legacy lighting technologies?
Not exactly but It might be possible to provide enough optical power for your application at specific wavelength ranges.  White LEDs do not replicate the spectrum of legacy lighting technologies but can appear very similar to the human eye.  


What color temperature are your white LEDs and are other color temperatures available?
It varies from product to product but generally in the cool white range between 5000-7000 deg Kelvin.  We will consider requests for other color temperatures. 


Can an LED light be supplied with peak wavelength specified at a specific, single nanometer?
Unfortunately we cannot.  LEDs can only be ordered from our suppliers in bins of peak wavelength and optical power.  The peak wavelength range of these bins are generally +/-5 or +/-10 nm wide.   To get narrower bins is sometimes possible.  However, to get a narrower peak wavelength range requires further sorting from larger lot of LEDs purchased.  Ultimately, it would be very difficult to control the wavelength to within a single nanometer due to fluctuations with current and temperature.  If those are tightly controlled it may be possible.


Does the wavelength change over time?
For red or infrared LEDs the wavelength generally increases.  For green LEDs, the wavelength generally increases at lower currents.  Blue LEDs are relatively stable and change very little.  Thermal management is key.  Once the system reaches steady state temperature its wavelength will remain stable unless the current is changed.   


What is the lifetime of your LED products?
MTBF is not generally used in the LED industry because LEDs when used properly, that is with good heat sinking and without excessive current, don’t generally catastrophically fail.  Their light output will gradually decrease from the initial maximum.  LED lifetime is generally defined by the time it takes for the maximum optical power to decrease to 70% of its original.  This is termed “L70” by the larger LED industry.  
 
We rely on the specification of the LEDs run at rated current by our vendors to estimate lifetime.  The lifetime will be at least 50,000 hours and could be 100,000.   Our lights feature better thermal management than is typically assumed so even when run continuously at higher currents we expect to achieve 50,000 hours at minimum.  Strobing or intermittent operation generally increases the effective lifetime because heat is not built up and the light is off more often than on.  MTBFs will be 100,000 hours or more.


Can your LED products be strobed?
Yes.  
 
Strobing is generally done to stop motion in a machine vision application or produce a very brief pulse of light much brighter than at the rated current.  Remember an overdriven pulse that might be 10 times brighter will put out the same amount of light as the light would if left on at the original current for 10 times longer.  Intensity in a camera exposure or process is directly proportional to the length of the time the light is on and the amount of light emitted per unit time.  The main function of strobing is to stop motion with fast well timed pulses.  Overdriving allows for either adequate exposure levels or shorter pulses and therefore faster processes.  Strobing or simple on/off control also reduces the affects of heat on the lights.
 
Strobing or frequent on/off operation does not damage LED lights so long as it is done properly.  However, it is very easy to damage LED lights by strobing them if it is done improperly.  All strobing is done at your risk.  
 
The LEDs themselves have response times of the order of nanoseconds and track the power supplied to them extremely closely.   However, the relation between light output and current is not linear at high currents.  The efficiency of the LED decreases and effectually rolls over.  If you are pulsing in this regime you have a high risk of damaging the light.  For support in determining the maximum safe strobe current for your application contact us.
 
We offer strobe controllers that can strobe as fast as a microsecond and offer programmable deterministic currents, pulse widths, delay, and duty cycle limits.   With these or your own current controller it is often possible to overdrive our lights by as much as 10-15 times safely.  Note that high pulse currents are only safe for short pulse widths, generally a millisecond or less, and low duty cycles, generally 10% or less.
 
The COBRA Slim linescan light features optional strobing functionality.  
 
The SpecBright product family, when configured for current control, can be safely overdriven many times.  The exactly amount depends on the wavelength, thermal management, pulse width, and duty cycle.  SpecBright 24VDC configured lights should not be overdriven though they can be strobed for very short pulses without risk.  
 
Unfortunately we cannot guarantee pulsed output intensities and overdriven pulsing is done at the users risk.   


How bright are your LED products in Watts like my fluorescent or halogen lights are rated?
While many high brightness LEDs available from major manufacturers are described as products as 1W, 3W, or 5W devices this is not a good description of how an LED light will perform, just as it is not a good description of how a fluorescent or halogen light will perform.  This is a description of the electrical power draw, only a fraction of which is converted to optical power and a fraction of that reaches where it is needed.  
 
We specify our products or try to define specifications for custom designs in Watts per square meter (W/m2) as projected over a given area at specific distance from the source.   That being said our lights or designs produce under a Watt of optical power to several 100 Watts of optical power.  Direct comparison with legacy lighting technologies is difficult and requires very controlled testing.  However, our customers have confirmed we make lights that can be brighter than halogen and other lighting technologies.


Can I power your lights from 24VDC?
Yes, almost all of our standard products can be configured to be powered from 24VDC.  The only exception is the SpecBright Spot light product which requires a constant current controller such as our CMP-M-400.  That controller takes 24VDC input.


Do you offer lights configured for constant current control?
Yes, all of our lights can be configured for constant current control.  The COBRA product family features an integrated light specific current controller.  The SpecBright products can all be configured as constant current controlled lights for no extra cost as standard.  While this requires an extra part in addition to the power supply--a current controller such as our CMP-M-400 controller, a CMS strobe controller, or your own controller—the benefits are potentially higher brightness, more linear intensity control, overdriving potential, less heat generated, and better stability.


The light is hot to the touch. Is this bad?
The body of the light needs to be kept below 45 degrees Celsius. If the body of the light is too hot to hold onto the light needs better heat sinking or other thermal management.  Lower the current, add a fan, and/or add a heat sink.  We offer optional modular heat sink accessories for the SpecBright range.  Your fixturing if it is a metal such as aluminum with sufficient surface area can also function as the heat sink.  We offer modular heat sinks because smaller lights are easier to integrate and in some application either the fixturing is an adequate heat sink or the light is run a low enough power or duty cycle (strobed) that heat sinking is not a concern.


Do I need to order the optional heat sink for accessory with a SpecBright?
If you are running the light at or near full power for a few minutes or longer you need heat sinking.  The body of the light must be kept below 45 degrees Celsius.  If you attach our heat sink accessory you can be assured that for normal factory environments the light will be within safe operating limits.  Your own fixturing may also be just as good.  We made the heat sinks modular to allow you the flexibility when integrating our lights into your system.


Your light has a big heat sink on it. Does that mean it is poorly designed and likely to fail prematurely?
The opposite is true.  The fact that our lights get hot is a sign that the thermal design is very good.  It means that the heat is getting away from the LEDs themselves which is what leads to premature failure, shorter lifetime, and short term optical instability (optical power and wavelength).  For situation where the LEDs are being run high currents continuously such as in our COBRA line scan light product range a substantial heat sink, possibly with fans, is required to dissipate the heat.   Similarly, if the SpecBrights are being run at or near full power for more than a few minutes they should be attached to a heat sink such as our modular heat sink accessories.  If the case temperature is 45 degrees Celsius or higher, too hot to hold on to, the lights need an adequate heat sink.


LED eye safety
LED lights do not fall under laser safety classifications by regulation though they have in the past and those are sometimes still used. LED photo-biological safety regulations are evolving in some countries. Most visible and infrared LED lights are considered to be eye safe (Class 1 or Class 2).   For focused high power Infrared lights such as the COBRA series, precaution should be taken not to stare into the light and eye protection is recommended.  Ultra violet lights of any type should not be considered safe.  Eye protection should be worn at all times.


3D PRO Laser

Cobra Slim

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