Depicted here are typical reflectivity plots for aluminum- and gold-coated surfaces (without the protective window) as well as the AR Coating Curve for the protective 5^o wedge. The data for the unprotected aluminum and gold coatings was obtain with using unpolarized light that was incident at 45 degrees.

Introduction:
Adaptive optics (AO) is a rapidly growing multidisciplinary field encompassing physics, chemistry, electronics, and computer science. AO systems are used to correct (shape) the wavefront of a beam of light. Historically, these systems have their roots in the international astronomy and US defense communities. Astronomers realized that if they could compensate for the aberrations caused by atmospheric turbulence, they would be able to generate high resolution astronomical images; with sharper images comes an additional gain in contrast, which is also advantageous for astronomers since it means that they can detect fainter objects that would otherwise go unnoticed. While astronomers were trying to overcome the blurring effects of atmospheric turbulence, defense contractors were interested in ensuring that photons from their high-power lasers would be correctly pointed so as to destroy strategic targets. More recently, due to advancements in the sophistication and simplicity of AO components, researchers have utilized these systems to make breakthroughs in the areas of femtosecond pulse shaping, microscopy, laser communication, vision correction, and retinal imaging.  Although dramatically different fields, all of these areas benefit from an AO system due to undesirable time-varying effects. 

Typically, an AO system is comprised from three components: (1) a wavefront sensor, which measures these wavefront deviations, (2) a deformable mirror, which can change shape in order to modify a highly distorted optical wavefront, and (3) real-time control software, which uses the information collected by the wavefront sensor to calculate the appropriate shape that the deformable mirror should assume in order to compensate for the distorted wavefront. Together, these three components operate in a closed-loop fashion. By this, we mean that any changes caused by the AO system can also be detected by that system. In principle, this closed-loop system is fundamentally simple; it measures the phase as a function of the position of the optical wavefront under consideration, determines its aberration, computes a correction, reshapes the deformable mirror, observes the consequence of that correction, and then repeats this process over and over again as necessary if the phase aberration varies with time. Via this procedure, the AO system is able to improve optical resolution of an image by removing aberrations from the wavefront of the light being imaged.

The Wavefront Sensor:
The role of the wavefront sensor in an adaptive optics system is to measure the wavefront deviations from a reference wavefront. There are three basic configurations of wavefront sensors available: Shack-Hartmann wavefront sensors, shearing interferometers, and curvature sensors. Each has its own advantages in terms of noise, accuracy, sensitivity, and ease of interfacing it with the control software and deformable mirror. Of these, the Shack-Hartmann wavefront sensor has been the most widely used.

A Shack-Hartmann wavefront sensor uses a lenslet array to divide an incoming beam into a bunch of smaller beams, each of which is imaged onto a CCD camera, which is placed at the focal plane of the lenslet array. If a uniform plane wave is incident on a Shack-Hartmann wavefront sensor (refer to Fig. 1), a focused spot is formed along the optical axis of each lenslet, yielding a regularly spaced grid of spots in the focal plane. However, if a distorted wavefront (i.e., any non-flat wavefront) is used, the focal spots will be displaced from the optical axis of each lenslet. The amount of shift of each spot’s centroid is proportional to the local slope (i.e., tilt) of the wavefront at the location of that lenslet. The wavefront phase can then be reconstructed (within a constant) from the spot displacement information obtained (see Fig. 2).

The four parameters that greatly affect the performance of a given Shack-Hartmann wavefront sensor are the number of lenslets (or lenslet diameter, which typically ranges from ~100 – 600 μm), dynamic range, measurement sensitivity, and the focal length of the lenslet array (typical values range from a few millimeters to about 30 mm). The number of lenslets restricts the maximum number of Zernike coefficients that a reconstruction algorithm can reliably calculate; studies have found that the maximum number of coefficients that can be used to represent the original wavefront is approximately the same as the number of lenslets. When selecting the number of lenslets needed, one must take into account the amount of distortion s/he is trying to model (i.e., how many Zernike coefficients are needed to effectively represent the true wave aberration). When it comes to measurement sensitivity θ_min and dynamic range θ_max, these are competing specifications (see Fig. 3 below). The former determines the minimum phase that can be detected while the latter determines the maximum phase that can be measured. 

The Shack-Hartmann wavefront sensor is capable of providing information about the intensity profile as well as the calculated wavefront. Be careful not to confuse these. The left-hand frame of Fig. 4 shows a sample intensity profile, whereas the right-hand frame shows the corresponding wavefront profile. It is possible to obtain the same intensity profile from various wavefuncton distributions.

The Deformable Mirror:
The deformable mirror (DM) changes shape in response to position commands in order to compensate for the aberrations measured by the Shack-Hartmann wavefront sensor (refer to the Types of Aberrations tab to learn more about the aberrations that the DM can correct).  Ideally, it will assume a surface shape that is conjugate to the aberration profile (see Fig. 5). In many cases, the surface profile is controlled by an underlying array of actuators that move in and out in response to an applied voltage.  Deformable mirrors come in several different varieties, but the two most popular categories are segmented and continuous (see Fig. 6). Segmented mirrors are comprised from individual flat segments that can either move up and down (if each segment is controlled by just one actuator) or have tip, tilt, and piston motion (if each segment is controlled by three actuators).  These mirrors are typically used in holography and for spatial light modulators. Advantages of this configuration include the ability to manufacture the segments to tight tolerances, the elimination of coupling between adjacent segments of the DM since each acts independently, and the number of degrees of freedom per segment. However, on the down side, the regularly spaced gaps between the segments act like a diffraction pattern, thereby introducing diffractive modes into the beam. In addition, segmented mirrors require more actuators than continuous mirrors to compensate for a given incoming distorted wavefront. To address the optical problems with segmented DMs, continuous faceplate DMs (such as those included in our AO Kits) were fabricated. They offer a higher fill factor (i.e., the percentage of the mirror that is actually reflective) than their segmented counterparts. However, their drawback is that the actuators are mechanically coupled. Therefore, when one actuator moves, there is some finite response along the entire surface of the mirror. The 2D shape of the surface caused by displacing one actuator is called the influence function for that actuator.  Typically, adjacent actuators of a continuous DM are displaced by 10-20% of the actuation height; this percentage is known as the actuator coupling.  Note that segmented DMs exhibit zero coupling but that isn’t necessarily desirable.

Figure 7 (left frame) shows a screen shot of a cross formed on the 12 x 12 actuator array of the DM included with the adaptive optics kit. To create this screen shot, the voltages applied to the middle two rows and middle two columns of actuators were set to cause full deflection of the mirror membrane. In addition to the software screen shot depicting the DM surface, quasi-dark field illumination was used to obtain a photograph of the actual DM surface when programmed to these settings (see Fig. 7, right frame)

The Control Software:
In an adaptive optics setup, the control software is the vital link between the wavefront sensor and the deformable mirror. It converts the wavefront sensor’s electrical signals, which are proportional to the slope of the wavefront, into compensating voltage commands that are sent to each actuator of the DM. The closed-loop bandwidth of the adaptive optics system is directly related to the speed and accuracy with which this computation is done, but in general, these calculations must occur on a shorter time scale than the aberration fluctuations. 

In essence, the control software uses the spot field deviations to reconstructs the phase of the beam (in this case, using Zernike polynomials) and then sends conjugate commands to the DM. A least-squares fitting routine is applied to the calculated wavefront phase in order to determine the effective Zernike polynomial data outputted for the end user. Although not the only form possible, Zernike polynomials provide a unique and convenient way to describe the phase of a beam. These polynomials form an orthogonal basis set over a unit circle with different terms representing the amount of focus, tilt, astigmatism, comma, et cetera; the polynomials are normalized so that the maximum of each term (except the piston term) is +1, the minimum is –1, and the average over the surface is always zero.  Furthermore, no two aberrations ever add up to a third, thereby leaving no doubt about the type of aberration that is present.

Monochromatic Aberrations

There are five primary monochromatic aberrations, which can be further divided into two subgroups: those that deteriorate the image (spherical aberration, coma, and astigmatism) and those that deform the image (field curvature and distortion). These aberrations are a direct result of departures from first-order (i.e., sinθ≈θ) theory, which assumes the light rays make small angles with the principal axis. As soon as one wants to consider light rays incident on the periphery of a lens, the statement sinθ≈θ, which forms the basis of paraxial optics, is no longer satisfactory and one must consider more terms in the expansion:

The five primary monochromatic aberrations were first studied by Ludwig von Seidel, and hence, they are frequently referred to as the Seidel aberrations. Please note that since the expansion of sinθ is an infinite sum, the five monochromatic aberrations discussed below are not the only ones possible; there are additional higher-order aberrations that make smaller contributions to image degradation. The surface of the deformable mirror can be altered to accommodate all of these types of monochromatic aberrations.

1) Spherical Aberrations

For parallel incoming light rays, an ideal lens will be able to focus the rays to a point on the optical axis as shown in Fig. 1a; consequently, under ideal circumstances, the image of a point source that is located on the optical axis will be a bright circular disk surrounded by faint rings (see the Airy diffraction pattern shown in Fig. 1b). However, in reality, the light rays that strike a spherical converging lens far from the principal axis will be focused to a point that is closer to the lens than those light rays that strike the spherical lens near the principal axis (see Fig. 1c). Consequently, there is no single focus for a spherical lens, and the image will appear to be blurred; instead of having an Airy diffraction pattern in which nearly all the light is contained in a central bright circular spot, spherical aberration will redistribute some of the light from the central disk to the surrounding rings (see Fig. 1d), thereby reducing image contrast. Whenever spherical aberration is present, the best focus for an uncorrected lens will be somewhere between the focal planes of the peripheral and axial rays. Please note that spherical aberration only pertains to object points that are located on the optical axis.

2) Coma

Coma, or comatic aberration, is an image-degrading aberration associated with object points that are even slightly off axis. When an off-axis bundle of light is incident on a lens, the light will undergo different amounts of refraction depending on where it strikes the lens (see Fig. 2a); as a result, each annulus of light will focus onto the image plane at a slightly different height and with a different spot size (see Fig. 2b), thereby leading to different transverse magnifications. The resulting image of a point source, which is shown in Fig. 2c, is a complicated asymmetrical diffraction pattern with a bright central core and a triangular flare that departs drastically from the classical Airy pattern shown in Fig 1b above. The elongated comet-like structure from which this type of aberration takes its name can extend either towards or away from the optical axis depending on whether the comatic aberration is negative or positive, respectively. Due to the asymmetry that coma causes in images, many consider it to be the worst type of aberration.   

3) Astigmatism

Astigmatism, like coma, is an aberration that arises when an object point is moved away from the optical axis. Under such conditions, the incident cone of light will strike the lens obliquely, leading to a refracted wavefront characterized by two principal curvatures that ultimately determine two different focal image points. Figure 3a shows the two planes one needs to consider: the tangential (also known as the meridional) plane and the sagittal plane; the tangential plane is defined by the chief ray (i.e., the light ray from the object that passes through the center of the lens) and the optical axis, while the sagittal plane is a plane that contains the chief ray and is perpendicular to the tangential plane. In addition to the chief light ray, Fig. 3a also shows two other off-axis light rays, one passing through the tangential plane and the other passing through the sagittal plane. For complex multi-element lens systems (e.g., microscope objective or ASOM system), the tangential plane remains coherent from one end of the system to the other while the sagittal plane usually changes slope as the chief ray’s propagation direction is altered by the various components in the lens system. Consequently, in general, the focal lengths associated with these planes will be different (see Fig. 3b). If the sagittal focus and the tangential focal points are coincident, then the object point is on axis and the lens is free of astigmatism. However, as the amount of astigmatism present increases, the distance between these two foci will also increase, and as a result, the image will lose definition around its edges. The presence of astigmatism will cause the ideal circular point image to be blurred into a complicated elongated diffraction pattern that appears more linelike when more astigmatism is present (see Figs. 3c and 3d).

4) Field Curvature 

For most optical systems, the final image must be formed on a planar surface; however, in actuality, a lens that is free of all other off-axis aberrations creates an image on a curved surface known as a Petzval surface. This nominal curvature of this surface, which is known as the Petzval curvature, is the reciprocal of the lens radius. For a positive lens, this surface curves inward towards the object plane, whereas for a negative lens, the surface curves away from that plane. The field curvature aberration arises from forcing a naturally curved image surface into a flat one. For the image, the presence of field curvature makes it impossible to have both the edges and central region of the image be crisp simultaneously. If the focal plate is shifted to the vertex of the Petzval surface (Position A in Fig. 4), the central part of the image will be in focus while the outer portion of the image will be blurred, making it impossible to distinguish minor structural details in this outer region. Alternatively, if the image plane is moved to the edges of the Petzval surface (Position B in Fig. 4), the opposite effect occurs; the edges of the image will come into focus, but the central region will become blurred. The best compromise between these two extremes is to place the image plane somewhere in between the vertex and edges of the Petzval surface, but regardless of its location, the image will never appear sharp and crisp over the entire field of view.

5) Distortion 

The last of the Seidel aberrations is distortion, which is easily recognized in the absence of all other monochromatic aberrations because it deforms the entire image even though each point is sharply focused. Distortion arises because different areas of the lens usually have different focal lengths and magnifications. If no distortion is present in a lens system, the image will be a true magnified reproduction of the object (see Fig. 5b). However, when distortion is present, off-axis points are imaged either at a distance greater than normal or less than normal, leading to a pincushion (see Fig. 5a) or barrel (see Fig. 5c) shape, respectively.

Chromatic Aberrations

The monochromatic aberrations discussed above can all be compensated for using a deformable mirror such as the one included in these adaptive optics kits. However, when a broadband light source is used, chromatic aberrations will result. Since a DM cannot compensate for these aberrations, we will only briefly mention them here. Chromatic aberrations, which come in two forms (i.e., lateral and longitudinal), arise from the variation of the index of refraction of a lens with incident wavelength. Since blue light is refracted more than red light, the lens is not capable of focusing all colors to the same focal point; therefore, the image size and focal point for each color will be slightly different, leading to an image that is surrounded by a halo.  Generally, since the eye is most sensitive to the green part of the spectrum, the tendency is to focus the lens for that region; if the image plane is then moved towards (away from) the lens, the periphery of the blurred image will be tinted red (blue).

Introduction
Off-axis scanning is frequently used in many imaging techniques including Optical Coherence Tomography (OCT), Confocal Microscopy, and Adaptive Scanning Optical Microscopy (ASOM). Without adaptive optics, images obtained using these techniques will suffer from the off-axis aberrations discussed in the Types of Aberrations tab, thereby requiring one to choose between resolution and field of view. However, by using a deformable mirror, this tradeoff is overcome. To learn more about how a deformable mirror works and its role in an adaptive optics system, please see the Tutorial tab.

Figure 2 shows a schematic of the ASOM scanner lens assembly (SLA). Unlike a traditional microscope objective, which must image onto a flat surface, the ASOM allows for a curved image field (i.e., the natural image field shape for a lens – refer to the Field Curvature Section under the Types of Aberrations tab), thereby greatly simplifying the optical design and number of lens elements necessary. The figure shows four different scan angle positions. The blue lines represent on-axis scanning, whereas the green, red, and yellow lines correspond to various off-axis scan angles. For each scan angle illustrated, the wavefront distortion as a function of linear displacement from the central position on the image tile of the wavefront sensor is given.

Although the large aperture scan lens and overall system layout are specifically designed to deal with field curvature, all other off-axis aberrations, such as coma and astigmatism (see the Types of Aberrations tab for a detailed discussion), are still present in the ASOM system. These aberrations are compensated for at each individual field position throughout the scanner’s range by a deformable mirror. Figure 3 shows the optimal DM shape for a given angular position of the high speed steering mirror.

Figure 3. The angular position of the 2D steering mirror defines the observable field position. Here, the various mirror positions map out the image at five points along the y-axis. For each angular position of the high speed steering mirror shown in frame (a), the corresponding optimal deformable mirror shape is shown in frame (b). Note that the DM topology configuration necessary to correct the image at each field position is not trivial.

In addition to the WFS150-5C Shack-Hartmann Wavefront Sensor, your choice of an Al- or Au-Coated Mini- or Multi-DM deformable mirror, and control software (Windows XP Compatible), these adaptive optics kits also include a source, all collimation/imaging optics, and all mounting hardware necessary to build the layout depicted in the schematic below. Figure 1. Schematic showing the major components included with the AOK1-UM01, AOK1-UP01, AOK2-UM01, and AOK2-UP01 Adaptive Optics Kits. L, M, DM, BS, and BD refer to lens, mirror, deformable mirror, beamsplitter, and beam dump, respectively. The "X" marks the position of the CB1 U-bench, which is also the location of an image plane in the setup; thus, if desired, a user-supplied sample can be inserted at this location. Figures 2 and 3 below are photographs showing two different views of an assembled AO Kit. The cage components are divided into three pre-aligned pieces that need to be arranged on a user-supplied breadboard: two sections of preassembled cage components are used together to image a beam waist onto the DM surface and a third preassembled cage system is used to image a beam waist onto the Shack-Hartmann wavefront sensor. If you are not familiar with Thorlabs' 30 mm cage assemblies, they consist of cage-compatible components that are interconnected with cage rods. Each cage component features four tapped holes with center-to-center spacings of 30 mm, and they are joined together into a cage system using Ø6 mm rigid steel cage rods of varying lengths. For this setup, cage rods with lengths of 1", 1.5", 3", and 6" were used. The reason for building a cage system is to ensure that the optical components housed inside the cage system have a common optical axis. Figure 2. An areal view of an AOK1-UM01 Adaptive Optics kit. Please note that the breadboard is not included with the purchase of an AO kit. The key components, which will be discussed in the text below, are numbered. The first two preassembled cage sections consist of the laser diode source, four 75 mm focal length lenses, two cage-compatible turning mirrors, and a U-shaped bench. The CPS180 Laser Diode Module (labelled as #1 in Fig. 2), which outputs ~1 mW of light at 635 nm, is housed inside a CP02 Cage Plate (#2 in Fig. 2) using an AD11F Ø11 mm-to-SM1 Adapter. Light exiting the module is centered within the cage system and on the surface of the DM using the adjustment knobs on the two KCB1 Right-Angle Cage-Compatible Kinematic Mounts (the first of which is labeled as #4 in Fig. 2), which house BB1-E03 Broadband Dielectric Mirrors; these mirrors have an antireflection coating for the 750 - 1100 nm range. A CPA1 alignment plate, which locates a small through-hole at the exact center of a cage assembly, is used to assist with this alignment. Please note that with the purchase of AOK1-UP01 or AOK2-UP01, the two BB1-E03 mirrors are replaced by two BB1-E02 mirrors, which have an antireflection coating for the 400-750 nm range. Two LA1608-B 75 mm focal length lenses (the first of which is housed in the HPT1 Translating Lens Mount labeled as #2 in Fig. 2 and the second of which is housed in the CP02 Cage Plate labeled as #3 in Fig. 2) are used to image a beam waist at the center of the CB1 30 mm Cage System U bench (represented by an X in Fig. 1 and labeled as #6 in Fig. 2 above). A sample can be placed in this image plane. Please note that the LA1608-B lenses used for the AOK1-UM01 and AOK2-UM01 are replaced by LA1608-A lenses with the purchase of an AOK1-UP01 or AOK2-UP01 adaptive optics kit. In either case, the first lens is placed ~94 mm from the source (since the collimation optic built into the laser diode module source has a focal length of ~19 mm), and the second lens is placed in the optical path so that it is ~150 mm after the first lens. Then, during the alignment process done at Thorlabs, fine adjustments are made to the lens locations by using an SI050 Shearing Interferometer to ensure the laser beam is collimated. Then, two more LA1608-B lenses (one is housed in the HPT1 mount labeled as #7 in Fig. 2 and the other in the CP02 mount labeled as #8 in the figure) are used to image a beam waist onto the DM (#9); by having a beam waist at the DM surface, the range of actuation needed to correct for any aberrations is minimized. All of these components are connected using ER Cage Rods to build a cage system, which ensures that a common optical axis is maintained. Since both KCB1 turning mirror mounts are internally threaded, four ERSCA Adapters must be used to connect them with cage rods. These adapters are visible in the foreground of Fig. 3. The DM is mounted onto a DM-KM1 Kinematic Mount (available only with this kit), which in turn is mounted on an RS2 Post and secured to the breadboard using an RB2 Post Base. The DM is placed on the breadboard such that it is located 75 mm after the fourth lens and so that the reflected beam makes as shallow of an angle as possible. In this case, the angle of reflection is ~35o. The third preassembled cage section consists of two more 75 mm focal length lenses, which are once again housed using an HPT1 Translating Lens Mount (#10 in Fig. 2) and a CP02 Cage Plate (#11 in Fig. 2). Two CP02B Cage Plate Adapters, which are mounted onto TR3 Posts and secured to the breadboard using UPH2 Universal Post Holders, are placed approximately 1/3 and 2/3 of the way between the lenses to support the weight of the cage components. These lenses are used to place the DM in a plane that is conjugate with the Shack-Hartmann lenslet array, thereby enabling the AO kit software to optimize the position of the DM actuators. This section of cage components is placed on the breadboard so that the first lens is located 75 mm after the DM. After exiting the third cage subassembly, a 92:8 pellicle beamsplitter (#12 in Fig. 2) is used to direct a small portion of the light to the last major component of the AO kit, the WFS150-5C Shack-Hartmann Wavefront Sensor (#13). The sensor is placed on a 1.6" x 1.0" KM100P Kinematic Platform Mount; a PM1 Small Clamping Arm is threaded into one of the #6-32 tapped holes on the platform, and then the clamp is used to hold the wavefront sensor housing in place. The kinematic mount is threaded onto a TR3 Post (Ø1/2" x 1.5" tall) and secured to the breadboard with a UPH2 Universal Post Holder.  To attenuate the amount of light entering the Shack-Hartmann wavefront sensor, an NE20A Mounted Ø1" Neutral Density Filter, which has an optical density of 2.0, is used. Since the sensor itself features internal C-mount threading and the ND filter is housed inside a 0.3" long SM1 (1.035"-40) lens tube, an SM1A9 C-Mount to SM1 Adapter is necessary to mate the ND filter to the front of the WFS150C. The portion of light transmitted by the beamsplitter can be blocked by a beam block (#14) that is constructed from an SM1A7 Alignment Blank that has been threaded into an LMR1 Lens Mount and onto a TR3 Post. The post can be secured to the breadboard using a UPH2 Universal Post Holder. Alternatively, the beam block can be removed and the light can be launched into an application. Figure 3. A photograph showing an alternative view of a preassembled Adaptive Optics Kit. Please note that a breadboard is not included with the purchase of AOK1-UP01, AOK1-UM01, AOK2-UP01, or AOK2-UM01.

AO Kit Component Pieces Item Qty. Photo WFS150-5C Shack-Hartmann Wavefront Senor 1 DM140-35-UP01, DM140-35-UM01, DM32-35-UM01, or DM32-35-UP01 Deformable Mirror 1 Source CPS180 Collimated Laser Module 1 LDS1 5V DC Regulated Power Supply 1 Optics LA1608-A 75 mm Focal Length Lens* 6 BB1-E02 Broadband Dielectric Mirror** 2 NE20A Mounted Ø1" Absorptive Neutral Density Filter 1 BP108 Pellicle Beamsplitter 1 Mechanics DM-KM1 Kinematic Mount (Sold in Kit Only) 1 KCB1 Right-Angle Kinematic 30 mm Cage Mount 2 HPT1 30 mm Cage-Compatible XY Translation Mount 3 CP02 Threaded 30 mm Cage Plate 4 CP02B Cage Plate Adapter 4 CB1 30 mm Cage System U Bench 1 LMR1 Lens Mount for Ø1" Optics 1 AD11F SM1 Adapter for Ø11 mm Collimators 1 SM1A9 C-Mount to SM1 Adapter 1 KM100BP Pellicle Kinematic Mount 1 KM100P Kinematic Prism Mount 1 PM1 Small Clamping Arm 1 UPH2 2" High Universal Post Holder 10 TR3 Ø1/2" x 3" Post 10 ER1 Ø6 mm x 1" Cage Rod 4 ER1.5 Ø6 mm x 1.5" Cage Rod 4 ER3 Ø6 mm x 3" | Cage Rod 4 ER6 Ø6 mm x 6" Cage Rod 12 ERSCA ER Rod Adapter 4 RB2 Adjustable Height Post Base 1 RS2 Ø1" x 1" Pillar Post Extension 1 Alignment Tools CPA1 30 mm Cage System Alignment Plate 1 SM1A7 SM1 Alignment Disk 1 *AOK1-UM01 contains LA1608-B. **AOK1-UM01 contains BB1-E03.

A Note about the Optics Included with the Adaptive Optics Kits:
The AOK1-UM01 (kit with gold-coated Multi-DM), AOK1-UP01 (kit with aluminum-coated Multi-DM), AOK2-UM01(kit with gold-coated Mini-DM), and AOK2-UP01 (kit with aluminum-coated Mini-DM) contain the same exact components with 3 exceptions. AOK1-UM01 and AOK2-UM01 contain a gold-coated DM (DM140-35-UM01 or DM32-35-UM01, respectively), two Ø1" broadband dielectric mirrors with antireflection coatings for the 750-1100 nm range, and six 75 mm focal length plano-convex lenses with antireflection coatings for the 650-1050 nm range. In contrast, the AOK1-UP01 and AOK2-UP01 contain an aluminum-coated DM (DM140-35-UP01 or DM32-35-UP01, respectively), two Ø1" broadband dielectric mirrors with antireflection coatings for the 400-750 nm range, and six 75 mm focal length plano-convex lenses with antireflection coatings for the 350-650 nm range. Although all kits ship with a 635 nm source, Thorlabs anticipates that in many cases, the end user will use our kit light source for testing purposes and then swap it out for a different light source. Hence, the optics have been matched to the AR-coating of the DM itself (i.e., the aluminum-coated DMs ship with optics for the visible range, whereas the gold-coated DMs ship with optics for the near IR spectral range).