3719 Warren Avenue Bellwood,
Illinois 60104 USA






How Does Acoustic Laser Beam Steering Compare to Other Methods of Laser Beam Steering?

Many methods have been developed for steering laser beams for various technological applications, including micromachining, microscopy and optical wireless communications. Each approach has its own set of advantages and disadvantages, so choosing the best method for your application is critical.

Optomechanical beam steering elements include AO deflectors, mirrors and liquid crystal (LC) phased arrays. Some techniques for beam steering involve large prisms that have high costs and power consumption as well.

Optical Phased Arrays

Laser beam steering using this approach involves recycling light signals through a single phase shifter multiple times to lower power consumption, thus enabling low-power operation with high speed and broadband low loss performance, as well as decreasing overall array operation power by factor of cycles recycled.

One way of accomplishing this goal is through optical phased arrays, commonly employed in modern fiber-optic systems. These arrays can either be passive, active, or hybrid types of structures.

Optic phased arrays generally consist of a source of coherent optical radiation which evanescently couples into a column waveguide and then into multiple row waveguides via an evanescent coupling process; any necessary couplers could then be manufactured via CMOS integration techniques such as silicon-on-insulator (SOI) technology.

Each pixel in an array contains a grating antenna element which emits a coherent optical beam in one specific direction. To avoid interference between second-order gratings and backreflections that could impede propagation of beam within phased array, these detuned periods slightly exceed second order grating periods to provide increased beam propagation efficiency.

Each pixel 130 is composed of an underlying pixel waveguide 132 formed using the same CMOS process used to form the column bus and row bus waveguides. This waveguide 132 can be composed of semiconductor materials like silicon or silicon nitride with dielectric claddings such as silicon oxide (SiOx).

To create the grating antenna element, the team used a sequence of partial silicon etching followed by full silicon etching to produce a groove which they then etched away to form the nanoantenna grating antenna element. Next, they implanted n and n+ dopings into this grating to enhance its spectral purity, an essential factor for optimal device performance.

To achieve their desired spectral purity, the team used resonant tuning of each grating element. A period of 720nm slightly detuned from that of second-order gratings was chosen to suppress back-reflections and ensure optimal output from each antenna element. Pixels were then organized on 64×64 grids at an approximate pixel pitch of about l0/2 where l0 represents wavelength of coherent optical beam.

Spatial Light Modulators

Spatial light modulators (SLMs) are devices used to manipulate the amplitude, phase or polarization of laser beams in space and time. Usually constructed out of transparent or reflective liquid crystal micro-displays, SLMs offer relatively affordable laser beam steering technology which can be utilized across a variety of applications.

Programmable devices are capable of acting like gratings, lenses, diffractive optical elements, apertures, masks and information processors/encryptors; their range of applications is vast yet only beginning to be explored.

Spatial light modulators (SLMs) are electronic devices designed to modulate light beams spatially and temporally using computer programs, either by writing specific patterns onto them directly or through real time control software programs. A spatial light modulator can be programmed with any pattern you choose – from writing custom code directly onto it to using software programs to control display.

SLM devices are electrooptical devices containing liquid crystal molecules as modulating material. Their alignment and birefringence enable this device to alter either the amplitude or phase of light beams in space and time.

SLMs are integral parts of many laser beam shaping systems, especially those employing an array of them to steer a beam in space and time. Furthermore, these devices can also be utilized as acoustic deflectors and optical tweezers.

Recently, we developed an electrically addressable silicon-based membrane spatial light modulator (DMD) specifically tailored for this application. The device allows phase modulation of an analog signal input to one SLM with up to 256 adjustable phase levels; making this method significantly more cost effective than conventional electrically addressable spatial light modulators (EASLMs) in this regard and capable of modulating various spectral bands simultaneously.

To understand the effect of SLM pixel pitch on spatial light modulation, we collected Mueller matrices from six distinct signal optical power (SOP) values of incident light. We observed that its modulation characteristics vary with respect to spatial locations for SLM displays while phase modulation remains constant.

Acoustic Deflectors

If you are using a laser system to pattern an integrated circuit (IC), then acousto-optic deflectors may be an effective and precise way to steer the laser beam. Compared with other methods of laser beam steering, acousto-optic beam steering provides fast and precise results.

Acousto-optic deflectors use high-frequency acoustic waves to modulate the refractive index of materials. This technique has been employed successfully since the 1990s for optical communications, spectroscopy and other purposes.

This type of deflector can be created out of any suitable material that emits an acoustic wave, such as silica or tellurium dioxide. When activated by an acoustic wave, its presence changes the refractive index of its material and forces laser beam to be deflected away from it.

Acoustic optic deflectors allow users to control the direction of an acoustic wave passing through it to produce various scan angles, providing greater diffraction efficiency – an essential performance indicator.

However, this diffraction efficiency may be restricted by an acoustic wave’s velocity which is usually limited. To overcome this hurdle, acousto-optic devices can be modified for higher diffraction efficiency with electronic driver power control of their acoustic wave source.

Based on its diffraction efficiency, acousto-optic laser beam steering can be utilized for many different applications. For instance, this method may be utilized for laser scanning, X-ray imaging and various forms of spectroscopy.

Acousto-optic techniques offer a wide variety of scanning angles that make them ideal for laser scanning applications that require fast, smooth, and accurate angular scanning.

Acoustic optical systems can also be utilized to produce patterns on IC substrates, which is especially advantageous for lithography systems that require precise patterns to ensure accurate placement of chips and vials on an IC substrate.

Acoustic laser steering is highly customizable and can produce various patterns on an integrated circuit substrate. For example, using deflectors and mirrors, laser systems can be tailored to create pixel patterns on an IC substrate.

Laser Beam Alignment

Laser beam alignment is a vital component of any laser system and can dramatically enhance performance. Unfortunately, however, such systems are complex and require special optical components and assemblies for proper functioning.

First, the laser diode beam must be collimated using either a collimating lens or fiber collimator to align properly. Collimation is essential as output from diode lasers can become very unstable if not collimated properly and could even change dramatically due to mechanical shock or instability with collimating optics.

As such, several manufacturers provide high-performance collimating optics for laser beam alignment. Many of them feature short focal length and precision that is unrivaled. Furthermore, collimating lenses may be constructed from materials resistant to dust buildup that could degrade beam quality.

Dependent upon the wavelength and requirements for its beam, an alignment laser’s output may be red, green or blue depending on its wavelength and requirements for its beam. A green output has the benefit of being visible to human eyes – ideal when needing visible beams in environments with strong lighting sources such as fluorescent bulbs.

Red laser output, however, is less visible due to human eyes’ decreased sensitivity for longer wavelengths.

Beam alignment may become challenging if a laser emitting long wavelength emissions is in a dark room with no direct line-of-sight between itself and another mirror.

An alignment laser with a transparent housing can provide a solution to this problem, whether made of thermoplastic or thermoset materials that resist dirt accumulation.

Opposed to other methods of laser beam steering, an alignment laser with transparent housing is simple to use and offers accurate results. Furthermore, its adaptability enables it to fit easily into multiple environments.
Scroll to Top