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N-BK7 Mounted Spherical Singlet Lens Kits![]()
Lenses and Cases LSC01 ![]() Please Wait
![]() Features
Thorlabs has taken its most popular Ø1/2", Ø1", and Ø2" N-BK7 spherical singlet lenses, housed them in laser-engraved SM-compatible lens tubes, and packaged them into kits. Each kit combines various lenses from our plano-convex, plano-concave, bi-convex, and/or bi-concave lines. The lenses, which are laser quality with a 40-20 scratch-dig surface finish to ensure minimal scattering, are available uncoated or with one of three broadband antireflection coatings: -A for the 350 - 700 nm range, -B for the 650 - 1050 nm range, or -C for the 1050 - 1620 nm range. See the Graphs tab for detailed coating information. Each black anodized lens housing features external SM05 (0.535"-40), SM1 (1.035"-40), or SM2 (2.035"-40) threading, making it directly compatible with the multitude of Thorlabs mounts and housings that feature this thread standard. In addition, the housings are laser engraved with the item number, lens type, focal length, and antireflection coating range (if applicable). In addition to the mounted N-BK7 lenses featured here, Thorlabs also offers a line of unmounted, N-BK7 spherical singlets with either a -A (350 - 700 nm) or -B (650 - 1050 nm) antireflection coating as well as a line of mounted, UVFS spherical singlets that are either uncoated or have a UV AR coating for the 290 - 370 nm range deposited on both sides.
The following tables display all of the lenses included with the lens kits sold on this page. Click "More" to see the full list of lenses included with each kit. Once expanded, each lens item number in the table can be clicked to view our standard support documents, more product information, and individual purchasing options. Ø1/2" N-BK7 Spherical Singlet Lens Kits
Ø1" N-BK7 Plano-Convex Spherical Singlet Lens Kits
Ø1" N-BK7 Bi-Convex Spherical Singlet Lens Kits
Ø1" N-BK7 Plano- and Bi-Convex Spherical Singlet Lens Kits
Ø1" N-BK7 Spherical Singlet Lens Kits
Ø2" N-BK7 Plano-Conxex Spherical Singlet Lens Kits
The N-BK7 lens kits on this page can be ordered uncoated or with AR coatings optimized for one of the following ranges: 350 - 700 nm (designated with -A), 650 - 1050 nm (designated with -B), or 1050 - 1620 nm (designated with -C). Our high-performance, multi-layer AR coatings have an average reflectance of less than 0.5% (per surface) across the specified wavelength ranges. Broadband coatings have a typical absorption of 0.25%, which is not shown in the reflectivity plots. ![]() Click to Enlarge Click Here for Raw Data The blue shaded region indicates the specified 650 - 1050 nm wavelength range for optimum performance. ![]() Click to Enlarge Click Here for Raw Data The blue shaded region indicates the specified 350 - 700 nm wavelength range for optimum performance. ![]() Click to Enlarge Click Here for Raw Data The blue shaded region indicates the specified 1050 - 1620 nm wavelength range for optimum performance.
Damage Threshold Data for Thorlabs' N-BK7 Singlet LensesThe specifications to the right are measured data for Thorlabs' AR-coated N-BK7 spherical single lenses. Damage threshold specifications are constant for a given coating type, regardless of the size of the lens.
Laser Induced Damage Threshold TutorialThe following is a general overview of how laser induced damage thresholds are measured and how the values may be utilized in determining the appropriateness of an optic for a given application. When choosing optics, it is important to understand the Laser Induced Damage Threshold (LIDT) of the optics being used. The LIDT for an optic greatly depends on the type of laser you are using. Continuous wave (CW) lasers typically cause damage from thermal effects (absorption either in the coating or in the substrate). Pulsed lasers, on the other hand, often strip electrons from the lattice structure of an optic before causing thermal damage. Note that the guideline presented here assumes room temperature operation and optics in new condition (i.e., within scratch-dig spec, surface free of contamination, etc.). Because dust or other particles on the surface of an optic can cause damage at lower thresholds, we recommend keeping surfaces clean and free of debris. For more information on cleaning optics, please see our Optics Cleaning tutorial. Testing MethodThorlabs' LIDT testing is done in compliance with ISO/DIS 11254 and ISO 21254 specifications. ![]() The photograph above is a protected aluminum-coated mirror after LIDT testing. In this particular test, it handled 0.43 J/cm2 (1064 nm, 10 ns pulse, 10 Hz, Ø1.000 mm) before damage. ![]()
According to the test, the damage threshold of the mirror was 2.00 J/cm2 (532 nm, 10 ns pulse, 10 Hz, Ø0.803 mm). Please keep in mind that these tests are performed on clean optics, as dirt and contamination can significantly lower the damage threshold of a component. While the test results are only representative of one coating run, Thorlabs specifies damage threshold values that account for coating variances. Continuous Wave and Long-Pulse LasersWhen an optic is damaged by a continuous wave (CW) laser, it is usually due to the melting of the surface as a result of absorbing the laser's energy or damage to the optical coating (antireflection) [1]. Pulsed lasers with pulse lengths longer than 1 µs can be treated as CW lasers for LIDT discussions. When pulse lengths are between 1 ns and 1 µs, laser-induced damage can occur either because of absorption or a dielectric breakdown (therefore, a user must check both CW and pulsed LIDT). Absorption is either due to an intrinsic property of the optic or due to surface irregularities; thus LIDT values are only valid for optics meeting or exceeding the surface quality specifications given by a manufacturer. While many optics can handle high power CW lasers, cemented (e.g., achromatic doublets) or highly absorptive (e.g., ND filters) optics tend to have lower CW damage thresholds. These lower thresholds are due to absorption or scattering in the cement or metal coating. LIDT in linear power density vs. pulse length and spot size. For long pulses to CW, linear power density becomes a constant with spot size. This graph was obtained from [1]. ![]() Pulsed lasers with high pulse repetition frequencies (PRF) may behave similarly to CW beams. Unfortunately, this is highly dependent on factors such as absorption and thermal diffusivity, so there is no reliable method for determining when a high PRF laser will damage an optic due to thermal effects. For beams with a high PRF both the average and peak powers must be compared to the equivalent CW power. Additionally, for highly transparent materials, there is little to no drop in the LIDT with increasing PRF. In order to use the specified CW damage threshold of an optic, it is necessary to know the following:
Thorlabs expresses LIDT for CW lasers as a linear power density measured in W/cm. In this regime, the LIDT given as a linear power density can be applied to any beam diameter; one does not need to compute an adjusted LIDT to adjust for changes in spot size, as demonstrated by the graph to the right. Average linear power density can be calculated using the equation below. The calculation above assumes a uniform beam intensity profile. You must now consider hotspots in the beam or other non-uniform intensity profiles and roughly calculate a maximum power density. For reference, a Gaussian beam typically has a maximum power density that is twice that of the uniform beam (see lower right). Now compare the maximum power density to that which is specified as the LIDT for the optic. If the optic was tested at a wavelength other than your operating wavelength, the damage threshold must be scaled appropriately. A good rule of thumb is that the damage threshold has a linear relationship with wavelength such that as you move to shorter wavelengths, the damage threshold decreases (i.e., a LIDT of 10 W/cm at 1310 nm scales to 5 W/cm at 655 nm): While this rule of thumb provides a general trend, it is not a quantitative analysis of LIDT vs wavelength. In CW applications, for instance, damage scales more strongly with absorption in the coating and substrate, which does not necessarily scale well with wavelength. While the above procedure provides a good rule of thumb for LIDT values, please contact Tech Support if your wavelength is different from the specified LIDT wavelength. If your power density is less than the adjusted LIDT of the optic, then the optic should work for your application. Please note that we have a buffer built in between the specified damage thresholds online and the tests which we have done, which accommodates variation between batches. Upon request, we can provide individual test information and a testing certificate. The damage analysis will be carried out on a similar optic (customer's optic will not be damaged). Testing may result in additional costs or lead times. Contact Tech Support for more information. Pulsed LasersAs previously stated, pulsed lasers typically induce a different type of damage to the optic than CW lasers. Pulsed lasers often do not heat the optic enough to damage it; instead, pulsed lasers produce strong electric fields capable of inducing dielectric breakdown in the material. Unfortunately, it can be very difficult to compare the LIDT specification of an optic to your laser. There are multiple regimes in which a pulsed laser can damage an optic and this is based on the laser's pulse length. The highlighted columns in the table below outline the relevant pulse lengths for our specified LIDT values. Pulses shorter than 10-9 s cannot be compared to our specified LIDT values with much reliability. In this ultra-short-pulse regime various mechanics, such as multiphoton-avalanche ionization, take over as the predominate damage mechanism [2]. In contrast, pulses between 10-7 s and 10-4 s may cause damage to an optic either because of dielectric breakdown or thermal effects. This means that both CW and pulsed damage thresholds must be compared to the laser beam to determine whether the optic is suitable for your application.
When comparing an LIDT specified for a pulsed laser to your laser, it is essential to know the following: LIDT in energy density vs. pulse length and spot size. For short pulses, energy density becomes a constant with spot size. This graph was obtained from [1].
The energy density of your beam should be calculated in terms of J/cm2. The graph to the right shows why expressing the LIDT as an energy density provides the best metric for short pulse sources. In this regime, the LIDT given as an energy density can be applied to any beam diameter; one does not need to compute an adjusted LIDT to adjust for changes in spot size. This calculation assumes a uniform beam intensity profile. You must now adjust this energy density to account for hotspots or other nonuniform intensity profiles and roughly calculate a maximum energy density. For reference a Gaussian beam typically has a maximum energy density that is twice that of the 1/e2 beam. Now compare the maximum energy density to that which is specified as the LIDT for the optic. If the optic was tested at a wavelength other than your operating wavelength, the damage threshold must be scaled appropriately [3]. A good rule of thumb is that the damage threshold has an inverse square root relationship with wavelength such that as you move to shorter wavelengths, the damage threshold decreases (i.e., a LIDT of 1 J/cm2 at 1064 nm scales to 0.7 J/cm2 at 532 nm): You now have a wavelength-adjusted energy density, which you will use in the following step. Beam diameter is also important to know when comparing damage thresholds. While the LIDT, when expressed in units of J/cm², scales independently of spot size; large beam sizes are more likely to illuminate a larger number of defects which can lead to greater variances in the LIDT [4]. For data presented here, a <1 mm beam size was used to measure the LIDT. For beams sizes greater than 5 mm, the LIDT (J/cm2) will not scale independently of beam diameter due to the larger size beam exposing more defects. The pulse length must now be compensated for. The longer the pulse duration, the more energy the optic can handle. For pulse widths between 1 - 100 ns, an approximation is as follows: Use this formula to calculate the Adjusted LIDT for an optic based on your pulse length. If your maximum energy density is less than this adjusted LIDT maximum energy density, then the optic should be suitable for your application. Keep in mind that this calculation is only used for pulses between 10-9 s and 10-7 s. For pulses between 10-7 s and 10-4 s, the CW LIDT must also be checked before deeming the optic appropriate for your application. Please note that we have a buffer built in between the specified damage thresholds online and the tests which we have done, which accommodates variation between batches. Upon request, we can provide individual test information and a testing certificate. Contact Tech Support for more information. [1] R. M. Wood, Optics and Laser Tech. 29, 517 (1998).
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