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I have a circuit fed by a 5V source which receives audio signals, amplifies them, and modulates an LED so the intensity of the LED changes with the voltage.

Ok so far so good. But what I want to do is to replace the LED with a laser diode. I tried and it behaves as LED.

In many websites I came across they are using a capacitor and diode when connecting a laser diode. Should I connect a laser diode in a different way than an LED? Why?

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Duplicate Question? electronics.stackexchange.com/questions/29218/… – The Photon Apr 4 '12 at 3:32
In another question you said you had a "laser module" instead of a raw laser diode. Can you provide a data sheet for your device? It would be very helpful for giving you a useful answer. – The Photon Apr 4 '12 at 3:34

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In simplest term no, you dont need to handle it differently

but

Laser diodes are usually much more sensitive than regular LEDs. Due to this you will usually see them driven by circuits with capacitors for voltage filtering/smoothing, signal diodes for polarity protection and some form of current limiting, either via a simple resistor or some other means.

So your diode might work but be aware that it might have a low life expectancy.

Resources:

Laser driver circuit

http://laserpointerforums.com/f42/diy-homemade-laser-diode-driver-26339.html

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All LEDs are Intensity proportional to current after the threshold current. THe ESR of the operating point is very low in power LEDs is about .5 Ohm per 1 watt device. or 5 ohm per 100 mW, so keep that into consideration with output driver impedance if using a voltage controlled current source such as one of the above suggested schematics.

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You are giving lots of information in the answers you've been posting; but many of your answers don't address the questions being asked. Here, OP didn't express any confusion about the behavior of LEDs. He asked, how is a laser different? – The Photon Apr 11 '12 at 15:53

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