5

Several useful notes

Microimmersion lenses (mIL) are made from chalcogenide glass with low

melting temperature (60-70

vertically,

pay

attention

to

heasinking

conditions

and

avoid

any

heaters close to the miL-LEDs.

Maximum

operating

current

is

defined

as

that

producing

Δt=10-20 K

overheating of the p-n junction relative to a heatsink temperature. We

recommend not exceeding 0.75

×Imax for long term operating devices.

In

certain

applications

it’s

important

to

know

that

in

addition

to

mid-IR

radiation

most optically pumped LEDs emit NIR pumping

radiation

λ≅0.87 μm as well (see graph on

the

right).

This

“parasitic”

emission

can

be

cut

off

by

filters

or

by

a

detector

window, e.g. by CdSb lens in TO-39 packed

LEDs.

0.80

0.85

0.90

0.95

0.0

0.5

1.0

Don’t touch the chip, connecting wires and miL surface.

Answers to frequently asked questions

Q: What are the advantages of the IL and mIL package?

A:

OP

LEDs

with

immersion

lenses

emit

radiation

within

small

spatial

angle, so it is easier to get a signal at some distance from the LED.

Q:

What

is

the

main

difference

between

LEDs

with

microimmersion

lens

(mIL) and LEDs with immersion lens (IL)?

A:

miL

LEDs

are

brighter/smaller

than

the

L-equipped

LEDs

and

thus

standard detectors with 1

close

“face-to-face”

schemes).

However,

IL

LEDs

are

more

stable

than

the mil LEDs with respect to heating and high drive currents.