| IR
LED's LMS manufactures and supplies a wide range of Infra red light emitting diodes with outputs at wavelengths in the 1.3 micron to 7.0 micron range. These long wavelengths LED's enable solid state optical pollution monitoring to give faster, more accurate information than traditional methods. Light emitting diodes (LED's) , mounted on TO-18 headers for room temperature operation, TO-8 headers with thermoelectric coolers and special dewars for liquid nitrogen cooling. The mounting of several LED's on a single TO-type header, each with a different wavelength, allows simultaneous monitoring of different pollutants. The benefits of infrared LED's include analytical instruments with no moving parts, reduced power consumption and solid state reliability. Infrared LED's operating at long wavelengths can be used in analytical instruments, portable monitors and medical equipment with all the advantages of LED technology. The different wavelengths are employed specifically for the following applications: 
LED-18: 1.8
micron LED for water vapour
LED-28: 2.8 micron LED for water vapour
LED-33: 3.3 micron LED for hydrocarbons
LED-34: 3.4 micron LED for hydrocarbons
LED-38: 3.8 micron LED for nitrous oxide
LED-42: 4.2 micron LED for carbon dioxide
LED-47: 4.7 micron LED for carbon
monoxide
LED-6:
6.0 micron LED Broad band IR sourceLED's Performance at Room Temperature
Unique
mid-infrared wavelength LED's offer a wide range of new applications
Sub-microsecond rise time - for faster system
response times
Solid state IR source - low power consumption, narrow bandwidt, bettere
liability LED's Applications
Measuring
impurities in liquids or gases
Monitoring trace gases in the
atmosphere
On-line control of chemical,
industrial, and horticultural processes
High frequency modulation for use
in communications and information processing Optics / Beam Divergence All LMS infrared LED's are surface emitting diodes, using a mesa structure. Typical emitting angle is ± 30°; this emitted beam can be focused to typically ± 10° by using either a quartz or sapphire lens. Usage Infrared LED's can operate at high frequencies, improving the signal-to-noise ratio, but beware of reduced lifetime of the LED if it exceeds the "envelope" of current and duty cycle. The duty cycle is typically only 2.5% - 5% to reduce self-heating and power consumption. Use a fast detector when designing with short duty cycles. Increase the frequency and number of averaged measurements to improve your signal-noise ratio. The LED substrate temperature will increase if you increase the power and duty cycle. Ensure that the LED is thermally connected through a good heatsink to improve lifetime and performance. Duty cycle, pulse current and frequency: all three of these parameters are adjustable with our LED-PG infrared emitter Pulse Generator. Cooling The efficiency (and output power) from these LED's increases rapidly with decreasing temperature. If the extra cost is justifiable, then either thermoelectrically cool or use a liquid nitrogen dewar. Remember that coolin shifts the peak to lower wavelengths. Power increases by (typically) fourfold when using a two stage thermoelectric cooler and tenfold when cooling from room temperature to liquid nitrogen temperature. Ensure that the LED is thermally connected through a good heatsink using heat sink compound to dissipate excess heat away and improve LED lifetime. Thermoelectric Cooling We offer single, two and three stage thermoelectric cooling; for temperature control, use our state of the art microprocessor controlled TE-TC temperature controller.
Liquid Nitrogen
Cooling
Package
Si Substrate
TO-18 with window / lens cap or TO-5 with
window cap for room temperature operation.
TO-8 with window cap for thermoelectrically
cooled operation.
Aluminium dewar for 77°K operation.
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