If a person wants to choose a laser diode driver for an application, it can very quickly become a multi-day project. The manufacturing and the design of fast pulsing current sources that are specific for semiconductor lasers is even now a highly fragmented market that is controlled by very few specialty companies. This means that it can be very challenging to find the companies making these drivers, and it’s even more difficult to get information from these companies that can help a person triangulate what product best suits them. This article will give a basic understanding of the important factors that must be kept in mind when buying a pulsed laser diode.
Pulsed Laser Diode Driver
A pulsed laser diode driver is basically a voltage-controlled current source that is constant and designed to deliver a set of repeatable current pulses over user-defined time intervals at a set output legal. The output to the laser is quantified in units of time and amplitude.
Typically, the only parameters that can be set are the pulsing time and the output current amplitude. There generally is not an adjustment for the output voltage. This is the available range of the output voltage coming from a current source that is constant to the load. This is the total voltage amount a current source can reach in attempting to produce the current that is desired. A constant current source’s job is to deliver a current amount that is precisely set, which meanest that as it does this, the sourcing of the voltage will follow Ohm’s law.
Most Important Specifications for Choosing a Pulsed Laser Diode Driver
Many people, when looking at the datasheet, skip from the photo of the product to the table of specifications that can help them filter to the product that suits them the best for what they want to use it for. Apart from the laser package style, here are five defined specifications that can help filter those selections down faster.
- Duty Cycle Limit (limited to a duty cycle of 50%)
- Frequency Range (generally Single Shot all the way to X MHz)
- Current Amplitude Range
- Pulse Width Range (microseconds, nanoseconds, or picoseconds)
- Compliance Voltage Range (generally in the range of 3v~10V)
It is recommended that you always begin with the laser diode’s package style for the first and primary filter for selection. This is intuitive and something that must be started with. Then the person can move backward to the pulser when trying to get the best fit dryer. There are specific laser package styles for pulsars that are commercially available. This would mean that there are interface mounting pins or pads that have been optimized for a TO-Can or butterfly package. Some of them even have high power bracket connector outputs that are used for high power fiber-coupled laser modules, i.e., 10s or even 100s of Watts. Impedance matching is often a very challenging task in fast pulsing applications, meaning that the interface from the pulser that is to the laser is often a significant variable during selection. It is recommended to move on if the manufacturer does not have photos that show the connection to the package style that the customer will be working with.
Considerations Regarding Spectral Emission when Pulsing Certain Diodes
When a person chooses a pulser, it is essential that they keep in mind the response type of the sort of laser diode that they intend to pulse. For example, when it comes to Fiber Bragg Grating (FBG) stabilized lasers, an inherent time period lag that is required for the laser itself to lock onto the Bragg locking element. The locking is almost immediate when it comes to a DBR of DFB, but there is a requirement of more than a hundred nanoseconds when it comes to an FBG based laser. When it comes to pulsing a Grating stabilized laser diode, what happens is that the first nanosecond is producing a broad emission spectrum, just as if there is no Bragg grating present. Some suppliers like Lumics give an intermediate solution offering the Bragg closer to the chip, thereby reducing the locking time lag down to a few nanoseconds.
Evaluation of Pulsed Mode Scope Plots is Essential
Generally, most of the manufacturers have readily available scope plots showing the pulse integrity that is measured on a high-frequency oscilloscope, i.e., 100s of MHz to GHz, and also with a fast GHz photodetector. These scops plots must always be based on a high rep. rate laser diode load that is not an electrical dummy load. It is recommended that one looks for scope plots that have been taken from powering a device in the same package style that one would want to use.
Manufacturers of Pulsed Drivers
Around the world, there are less than even ten companies that specialize in the manufacture of commercially available pulsers. Below are a few some diode drivers along with their manufacturers. Some of them can be bought directly from LaserDiodeControl.com, while others can be purchased from the manufacturer alone. The specifications are found on the site itself.
Manufacturer: AeroDiode an ALPhANOV spin-off
Current: 1.5 Amps
Minimum Pulse Width: 1 nanosecond
Description: Impedance matches LD Mount. USB Controlled. Nanosecond Pulses to CW. Compact.
Manufacturer: Analog Modules
Current: 50 Amps
Minimum Pulse Width: 600 nanosecond
Description: Pulse Width 600 nanoseconds to CW. Highly Compact OEM Driver.
Current: 20 Amps
Minimum Pulse Width: 200 nanosecond
Description: TO-Can Package Mounting Pads. Up to 1 Mhz Rep Rate.
Manufacturer: Meerstetter Engineering
Current: 30 Amps
Minimum Pulse Width: 200 nanosecond
Description: Highly Configurable. Lab, Production, and Field Use.
The current ranges of the diode drivers available on the site range from 5 mA to 500 Amps. The price range is from less than $500 to $20,000. Apart from the ones mentioned, the other brands are Aerodiode, ILX Lightwave, and Trimatiz. It is important to go through all of the specifications before a diode driver is bought online.
Laila Azzahra is a professional writer and blogger that loves to write about technology, business, entertainment, science, and health.