How To Choose Laser Products Accurately?

Since the advent of the world's first laser in 1960, Lasers have penetrated into various fields such as production, scientific research, medical care, and daily life. In various applications, the parameters of the laser directly determine the user's choice of laser light source. JTBYShield has compiled some parameter definitions of conventional lasers and briefly explained them here for your reference. We hope to help you find the laser product that suits you in the shortest time.

1. Output power

Like electrical energy, the light emitted by a laser is also an energy source, but it appears in the form of light energy. Therefore, the output power of a laser is the same as the output power of a power plant generator. It is a physical quantity that measures the laser energy output per unit time. Commonly used measurement units are milliwatt (mW), watt (W), kilowatt (kW), etc.

2. Power stability

Power stability represents the instability of laser output power within a certain period of time, which is generally divided into RMS stability and peak-to-peak stability.
What is the difference between RMS stability and peak-to-peak stability?
RMS stability: the ratio of the root mean square of all sampled power values during the test time to the average power value, describing the degree of dispersion of the output power from the average power value. On CNI laser's website, the laser power stability is RMS stability within 4 hours.
Peak-to-peak stability: the percentage of the difference between the maximum value and the minimum value of the output power and the average power value, which represents the variation range of the output power within a certain period of time.

CNI Laser Power Stability Test Chart

3. Beam quality factor (M2 factor)
The beam quality factor is defined as the ratio of the product of the laser beam waist radius and the beam far-field divergence angle to the product of the ideal fundamental mode beam waist radius and the fundamental mode divergence angle, that is.

How to evaluate the superiority of beam quality factor?
Beam quality will affect the focusing effect of the laser and the spot distribution in the far field. It is a parameter used to characterize the quality of the laser beam. The closer the actual laser beam quality factor is to 1, the closer the beam quality is to the ideal beam, and the better the beam quality will be. good. CNI laser semiconductor-pumped solid-state laser beam quality factor can be better than 1.1.

4. Light Spot (transverse mode)
The stable field distribution on a certain cross-section perpendicular to the laser propagation direction is called a transverse mode. The laser spot represents the transverse mode distribution. The transverse mode distribution is simulated through the CCD array to obtain some beam characteristics of the laser, as shown in the figure. The following shows the spot situation of a TEM00 Gaussian beam.

CNI Laser Spot Test Chart (TEM00)

In addition to the fundamental transverse mode (TEM00), there are other modes, as shown below:

Cylindrical Transverse Mold                Rectangular Transverse Mold

5. Spot Diameter
For the measurement of spot diameter, there are generally trepanation method, knife edge method, laser profile analyzer (CCD) measurement, etc.

Trench hole method: Since it is difficult to achieve concentricity between the hole and the beam in experiments, the accuracy is difficult to guarantee.
Laser profile analyzer (CCD) test: It can ensure the accuracy of the measurement results. The spot diameter in the software interface can provide the test results of four measurement methods (see Figure 3), of which the most widely used one is 13.5% of the peak value (1 /e2) is the boundary definition method. Although this test method has high accuracy, for high-power lasers, the CCD has a saturation phenomenon. If an attenuator is used, it may cause beam distortion.
Knife edge method: It is an ideal method for measuring the spot diameter of high-power lasers. Take the knife edge position coordinates x1 where the light power of the laser to be measured passes through the knife edge edge and accounts for 10% of the total power. Take the knife edge position coordinates x2 where the light power of the laser to be measured passes through the knife edge edge accounts for 90% of the total power. Spot diameter = 1.561×|x1- x2|(where 1.561 is the fitted value).  

Knife Edge Method for Measuring Spot Diameter

Is the light spot so small?
When measuring the spot diameter of visible light with a ruler or the human eye, why is the laser spot diameter obtained larger than that measured using a professional spot profile analyzer?
This is because the laser energy is strong and concentrated, and will diverge to a certain extent when it acts on the object. When using a spot profile analyzer to measure, the spot diameter at the peak intensity (13.5%) point is commonly used as the measurement result, so the measurement results obtained will be relatively Small.

6. Laser Modulation
Laser modulation uses light as a carrier to load signals onto the light and achieve signal transmission according to application requirements. Generally, modulation is divided into external modulation and internal modulation. External modulation refers to mechanical modulation or acoustic-optical modulation performed outside the laser; internal modulation refers to power-driven modulation. Internal modulation is divided into TTL modulation and analog modulation, as shown in the figure. Yellow CH1 is the input electrical waveform, and blue CH2 is the modulated optical waveform.

CNI Laser Modulation Waveform Diagram

TTL modulation: When a high and low level (0V or 5V) DC signal of a certain frequency is input to the external laser, the light is turned off when the low level is high, and the full power is output when the high level is high. The high level amplitude cannot be adjusted.
Analog modulation: The waveform and amplitude of the input signal can be freely adjusted, and the laser output power changes linearly with the input analog voltage signal.

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