Optical Filters Intro Windows Filter Specifications . 286 Filter Selection Guide. 288 Prisms Custom and Image Filters . 291 Interference Filters . 292 Lenses High Rejection Laser Line Filters . 302 Notch Filters . 304 Mirrors Edge Filters . 305 Beamsplitters Long Pass Filters. 306 Short Pass Filters . 307 Waveplates Variable Bandpass Filters . 308 Glass Substitute Filters . 309 Polarizers Color Process Filters . 310 Schott Color Glass . 312 Components Ultrafast Neutral Density Filters . 319 Variable Neutral Density . 322 Etalons Storage Cases. 324 Circular Filter Mount . 324 Filters Heat Control Filters Interferometer Hot Mirrors. 325 Accessories Cold Mirrors . 325 Dielectric Attenuators . 326 Mounts Spectrophotometer Appendix Calibration Filters. 328 ������� CCD System Equalizer Filters . 331 ���������� Index �������������� Optical Filters Intro Specifications Following is a short review of filter dependent variable determined by your in units of Optical Density (O.D.). Windows specifications to assist you in formulating requirements for center wavelength, full 1 Optical Density (O.D.) = — Log requirements for your particular width at half maximum, transmittance, T 10 application. CVI maintains a qualified and blocking. A CVI applications engineer where T= transmission. Prisms staff of applications engineers to assist you will be happy to help you with any in selecting the best product available at questions. The rejection range in nanometers must the minimum cost. accompany this specification. Out-of-Band Rejection Lenses Center Wavelength Filter Dimensions Out-of-Band Rejection (Blocking) is the Center Wavelength (CWL) is the amount of energy, outside the filter pass Filter dimensions are specified in inches arithmetic mean of the pass band band, transmitted through the filter. It is or millimeters, along with tolerances. Mirrors expressed in nanometers. For instance, often expressed as an absolute level, such Standard sizes are 0.50" Ø, 1.00" Ø, and a HeNe laser filter would have a center as 10-4, meaning there are no transmission 2.00" Ø. Standard interference filters are wavelength of 632.8nm. peaks outside the pass band exceeding mounted in a black anodized aluminum Center wavelength tolerance: 0.0001 T or 0.01% T. Values are specified ring to provide a higher quality filter. The Beamsplitters ± 20% of FWHM Percent Transmission ��� ��� ���� ���� Waveplates Percent Transmission is the amount of ����������� �� ����������� �� power received by the detector compared to the total power available. The Polarizers ������������ ����������� � � traditional formula is %T = I/Io x (100), where Io is the incident power and I is the ����������� transmitted power. ��� ��� Ultrafast Components ���������������������������� Bandpass ���������������������������� ���� ���� Bandpass is the width of the pass band, Etalons measured in nanometers, at the half- ����� ����� �������� power points of the pass band. It is often Figure 1. Typical Band Pass�������� Shape of a Figure 2. Typical Band Pass Shape of a expressed as Full Width at Half Maximum One Cavity filter. Two Cavity filter. Filters (FWHM). ��� ��� ���� ���� Tolerance: ± 20% of FWHM ����������� ����������� Bandpass Shape �� �� Accessories Interferometer Bandpass shapes can vary from triangular ����������� � � ����������� to nearly square. The number of cavities in a filter describes the overall spectral Mounts ����������� ��� ����������� shape. The more cavities the filter has, ��� the more square the band shape. Typical ���������������������������� ���������������������������� shapes for a one cavity, two cavity, three ���� ���� Appendix cavity, and five cavity filters are shown in Figures 1, 2, 3, and 4. Please note that for ����� ����� �������� custom filters, the number of cavities is a Figure 3. Typical Band Pass Shape of a Figure 4. Typical Band Pass�������� Shape of a Index Three Cavity filter. Five Cavity filter. 286 Americas (505) 296-9541 | Europe +44 (0) 1624 647000 | Asia +82 (0) 32 673-6114 | Order now at www.cvilaser.com Optical Filters Intro Specifications Windows thickness for these standard ring mounted Environmental Considerations Custom filters can be manufactured to filters is 0.25 inches. Custom sizes and withstand more than 20 cycles of Filters are sensitive to changes in thicknesses are available, please contact a MIL-STD-810C. environment, with temperature and Prisms CVI sales engineer for more information. humidity being the most critical factors. Cosmetics Variation of Wavelength with CVI interference filters are designed CVI strives to give all of its products a Incident Angle for operation at 23 degrees Celsius. pleasing appearance. However, total Lenses These filters can be used throughout CVI’s standard interference filters are elimination of pinholes, inclusions, the temperature range of -50 to +100 designed for use at normal incidence in microscopic scratches, and other degrees Celsius as long as thermal shock is collimated light. Certain characteristics imperfections would dramatically increase Mirrors avoided. (Thermal shock can be avoided of thin film interference filters change filter costs. Careful attention is given to if the change in filter temperature is less with incidence angle. Center wavelength, ensuring that these minor defects do not than five degrees Celsius per minute.) Beamsplitters the most important parameter of a filter, affect filter performance. Temperature change causes the center varies approximately as a cosine function, wavelength to shift approximately 0.02nm Packaging shifting towards shorter wavelengths with per degree Celsius. See Figure 5. increasing angle. The following equation CVI filter products are packaged to Waveplates may be used to determine the wavelength promote optimum shelf life. Unless the at a certain angle of incidence: customer makes special arrangements, ����� filter products will be delivered in our Polarizers no 2 2 standard packaging. Filters are packaged in λ = λo √ 1 − ( ) sin φ neff ����� a protective envelope which is impervious to moisture. This envelope is then purged Components where ������������������������������� ����� with nitrogen and heat sealed which Ultrafast λ = Wavelength at Angle of Incidence ��� ��� ��� ��� ���� ���� λ������ minimizes environmental damage. λo= Wavelength at Normal Incidence φ = Angle of Incidence Figure 5. Temperature Coefficient vs. Cleaning Method Etalons no = Refractive Index of External Medium Center Wavelength. Optical filters are fragile and must be neff=Effective Refractive Index of Filter handled with care. CVI’s filter products Long-term exposure to extreme humidity are cleaned and inspected for quality may cause filter deterioration. A CVI Filters assurance before they are shipped to the applications engineer can provide customer. These products should be Number of Cavities by CWL additional information on this subject. Interferometer handled by the edges to avoid any damage Accessories CWL HBW Number Range (FWHM) of Environmental Specifications to the optical surfaces. When cleaning (nm) (nm) Cavities becomes necessary, please follow the Humidity: MIL-STD-810F, 193-326 -- na recommended cleaning method below: Method 507, Procedure 1 330-396.1 10.0 3 Mounts 400-1064 1.5 1 Abrasion: MIL-C-48497, Fold a lens tissue to a size just larger that 400-1064 3.0 2 Para. 3.4.3.1 20 eraser rub the optic being cleaned. Spray the folded 400-1064 10.0 3 Adhesion: MIL-C-48497, edge of the tissue with isopropyl alcohol. Appendix 400-1064 25.0 5 Para. 3.4.1.1 tape test Gently wipe the surface of the filter with 400-1064 40.0 5 Cleanability: MIL-C-48497, a straight sweeping motion. Do not reuse 400-1064 70.0 5 Para. 3.4.2.2 solvents a contaminated tissue as damage to the 1070-2500 10.0 2 1070-2500 12.0 2 Surface Quality: 80-50 scratch-dig optical surface may occur. Repeat the Index > 2500 -- na process if necessary. Americas (505) 296-9541 | Europe +44 (0) 1624 647000 | Asia +82 (0) 32 673-6114 | Order now at www.cvilaser.com 287 Filters Intro Selection Guide Transmission Filters Windows Product Type FWHM Peak % T Blocking Applications ��� �������������������� High Rejection Filter 1.4-4.0nm 90% > 6 OD Fluorescence �� HRF Raman �� Prisms � 302 Laser line clean-up �� �� l �� � ��� ��� ��� ��� ��� ��� ��� ��������������� Lenses � Interference Filters 3nm, 10nm, 25nm, 12-60% 3-5 OD Laser line clean-up � F 40nm, 70nm � 292-301 �� Mirrors l � ��������� � � ��� ��� ��� ��� ��� ��� ��������������� ��� Beamsplitters �� Variable Bandpass Sets Sets of LPF and 80% 3 OD Fluorescence VPFS SPF filters to mix Raman �� � 308 and match for Laserline blocking �� �� l user selectable ��� �� ��� Waveplates bandpass � ��� ��� ��� ��� ��� ��� ��� ��������������� Polarizers Blocking Filters Product Type FWHM Peak % T Blocking Applications � Ultrafast �������������������� � Components Notch Filters 17nm 90% > 6 OD Fluorescence � RNF Raman � 304 Laserline blocking �� � l � Etalons � � ��� ��� ��� ��� ��� ��� ��� ��� ��������������� ��� ��������� Filters �� Color Process 100nm 75% 2 OD Fluorescence �� CP �� � ��� 310 �� �� l �� � Accessories Interferometer ��� ��� ��� ��� ��� ��� ��� ��� ��� ��� ��������������� ��� Color Glass 200-400nm > 80% up to 5 OD Attenuation �� Mounts CG Isolation of �� � 312-318 Broadband Source �� �� l ���������� �� � ��� ���� ���� ���� ���� ���� ���� Appendix ��������������� Index continued 288 Americas (505) 296-9541 | Europe +44 (0) 1624 647000 | Asia +82 (0) 32 673-6114 | Order now at www.cvilaser.com Filters Intro Selection Guide Windows Edge Filters Product Type