# I am buying a laser diode but cant understand some parameters

• hagopbul
In summary, when buying a Pulsed Laser Diode in Plastic Package 25 W Peak Power SPL PL90, it is important to consider the forward current of 40 A, reverse voltage of 3 V, and threshold current of 1 A. The threshold current is the minimal amount needed for lasing operation, and the emitted intensity depends on the current applied. It is important not to go above the maximum indicated value to avoid damaging the diode. The laser operates through an amplification process where the power in the form of infrared radiation is amplified, while the total power cannot exceed the amount of input power. The conversion efficiency from electrical energy to light output is typically below 30%.

#### hagopbul

i am buying Pulsed Laser Diode in Plastic Package 25 W Peak Power SPL PL90 and there is some parameters about semiconductors lasers...

Forward current = 40 A why all this current ?

then in the catalog Reverse voltage= 3 Volt

then they say the Threshold current = 1A ? what is the difference

when i by the diodes what current should i apply 40 or 1 !

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The threshold current is the the minimal current you need to apply to achieve lasing operation. From that point on the emitted intensity depends on the current you apply. You find the curve showing this in the upper left corner of the fourth page of your data sheet. The x-axis denotes the current you apply and the lower of the two courves shown there gives your output power. Now you can choose the current such that it suits your needs. However, you should not go too high. Going above the indicated maximum value might damage your diode.

thank you ...you helped me a lot ...but should the laser is amplification process ...but i am seeing that input power is mach higher than out put power ?

A laser operated far below threshold would basically just show spontaneous emission into many modes. Now the amplification means that one of these modes is preferred and amplified via stimulated emission at the expense of the other modes. So the benefit you get is huge emission from an amplified single mode. So you get some non-linearity in the input-output curve, but the power you apply to the laser as a whole is not amplified. If you got more out than you put in that would already violate conservation of energy. At room temperature the conversion efficiency from electrical energy to light output is usually not too high. While one can reach high values around 75%, typical values for semiconductor lasers that are actually on the market are way lower. 50% is already pretty much. Values below 30% are typical. However, that depends strongly on the wavelength range of interest.

hagopbul said:
thank you ...you helped me a lot ...but should the laser is amplification process ...but i am seeing that input power is mach higher than out put power ?
What gets amplified is the power that is in the form of infrared radiation at 905 nm (or whatever the laser wavelength is). Total power does not -- and cannot, ever -- exceed the amount of power input to the device.

## 1. What is a laser diode?

A laser diode is a type of semiconductor device that produces coherent and monochromatic light through the process of stimulated emission. It is commonly used in various applications such as telecommunications, laser pointers, and optical disc drives.

## 2. What do the parameters of a laser diode mean?

The parameters of a laser diode refer to the various characteristics and specifications of the device that determine its performance. These parameters include wavelength, output power, threshold current, and operating temperature, among others.

## 3. How do I choose the right laser diode for my application?

To choose the right laser diode, you need to consider the specific requirements of your application. This includes factors such as the desired wavelength, power output, and operating conditions. It is also helpful to consult with a specialist or refer to the manufacturer's datasheet for guidance.

## 4. What is the difference between single-mode and multimode laser diodes?

Single-mode laser diodes emit a single, well-defined beam of light, while multimode laser diodes emit multiple beams of light. Single-mode diodes are typically used for high-precision applications, while multimode diodes are more suitable for general-purpose uses.

## 5. How do I properly handle and operate a laser diode?

Proper handling and operation of a laser diode are crucial to its longevity and performance. It is important to follow the manufacturer's guidelines and precautions, such as wearing appropriate eye protection and avoiding excessive heat or current. It is also recommended to regularly clean and inspect the diode to ensure its optimal functioning.