Hi any one please help to modulation of a green laser circuit for laser pointer 120mA is threshold current 2.4v threshold voltage.maximum is 200mA


I need it for analog signal modulation for my degree project.

 

One may put a transformer in series with the laser current. This will allow you to modulate the laser in a number of ways.

The first thing to study is the laser data sheet.

 

its a laser pointer comes with 3V battery.
and characterised with 120mA threshold maximum around 250mA/.

is it possible to modulate with analog signal need current driver laser circuit

 

It all depends on what you want to do. To modulate with a analog signal can mean a lot of different things.

A laser pointer with a 3 volt battery can mean of lot of different things too.

Do you know what a data sheet is?

What kind of modulation do you want to use?

What is the modulating signal?

Would turning the laser on and off suffice? A key can modulate.

We don't know your details.

What degree are you working on?

 

sin wave (cw) modulation.
i given info about laser.....! then what is data sheet
engineering student for optical communication

 

Would turning the laser on and off suffice?

This likely won't work at 1MHz. A LD takes a bit of time to begin "lasing". The modulation depth should be just above the minimum lasing threshold for 100% modulation.

 

This likely won't work at 1MHz. A LD takes a bit of time to begin "lasing". The modulation depth should be just above the minimum lasing threshold for 100% modulation.

even less frequency is okay 500khz or 100kHz for what ever frequencies i need a circuit

 

I modulated an old HeNe laser tube by just putting a vacuum tube audio backwards in the HV line and feeding audio into the 8 Ohm side. It produced a high enough voltage to nicely modulate the laser. We did send audio quite a ways with it.

For a solid state laser it would be only a mater of impedance and using a capacitor because of the high frequency. It would be fun to see how high of a frequency a cheap laser pointer could do.

If you fed the laser through a resister to the midway current point you could see hpw much modulation was needed

 

need circuit

 

I have never modulated one. Other than a flashlight long ago. I was interested in seeing the device.

Can a laser be AMed? When we AM a carrier......not only does the amplitude change......sidebands are created. Can a laser generate sidebands? Does a laser make an envelope? Can we see a tint change with high levels of AM modulation?

How about FM? Can we FM a laser? What modulation index do we need to see a color change with modulation? Would we need to swing laser many MHz to see modulation?

And if the frequency of the laser changes with modulation.......is it still a laser? Or can we just turn a laser on and off?

Didn't mean to hijack the thread.

I believe the TS just wants to key a laser pointer....not a laser device.

 

Hi any one please help to modulation of a green laser circuit for laser pointer 120mA is threshold current 2.4v threshold voltage.maximum is 200mA


I need it for analog signal modulation for my degree project.

Google electro-optic amplitude modulator.

 

need circuit

Not sure what kind of modulation you want. But here is a simple amplitude or frequency modulator.

 

Not sure what kind of modulation you want. But here is a simple amplitude or frequency modulator.
View attachment 122824

Amplitude modulation
Sending an ofdm analog signal through laser
can u send the ltspice file

 

LZZ-101A 5mW 532nm Gypsophila Green Laser Pointer - Black (3 x AAA)

http://www.amazon.in/LZZ-101A-532nm...scsubtag=0a200e63-ff9e-4933-ac0f-a2f1ec6c22b4
does it work?

Moderators note: reduced font size as large fonts are like shouting

 

Amplitude modulation
Sending an ofdm analog signal through laser
can u send the ltspice file

Sorry, I don't know about ofdm. Maybe someone else does.
I didn't save the simulation, but I think I used all standard spice parts so you can enter it.

 

One may put a transformer in series with the laser current. This will allow you to modulate the laser in a number of ways.

The first thing to study is the laser data sheet.

In my opinion, the transformer's secondary in series with the laser's supply is the best suggestion offered so far in that if the laser is biased quiescently, through the transformer so that the laser will emit about half power, CW, when the modulator's contribution is nil then, when the transformer starts working, it'll add and subtract voltage / current into the LED, making its output brighter or dimmer.

Voila, amplitude modulation!

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