供应聚焦光栅 Focusing Gratings、自校准光栅 Self-Calibrating Gratings、相干光栅组 Coherent Grating Arrays

7. Focusing Gratings聚焦光栅LightSmyth’s family of flat-substrate focusing gratings are designed for use with external-cavity lasers. The gratings focus optical input signals while simultaneously spectrally dispersing them. The focusing function is incorporated into the gratings via holographic design principles using curved and variably-spaced grating lines. Integrating focus function with spectral dispersion through holography rather than by use of curved substrates or lenses reduces system component count and facilitates miniaturization.
 
Flat-substrate focusing gratings are also relevant to a broad range of applications in spectroscopy and general photonics. For example, fiber coupled miniature spectrometers may be build with minimum number of components: input fiber, focusing grating and output detector array. Such spectrometer may provide spectral coverage of several hundred nanometers and nm-level resolution on less than 15 x 15 mm footprint.
 
LightSmyth’s flat-substrate focusing gratings are optimized for implementation in external-cavity diode laser (ECDL) systems where they provide frequency-selective feedback and thus laser frequency stabilization and linewidth narrowing. The gratings are designed for ECDLs employing the Littrow configuration and focus the first-order diffracted beam back toward the laser providing tunable locking feedback. Grating focal lengths are short (3.75 mm) in order to facilitate large longitudinal mode spacing and to enable convenient wide-range single-mode tuning.
 
Grating groove depth and duty cycle are optimized to provide maximal diffraction efficiency. Each grating is a master, free from replication flaws. Grating surfaces are cleanable and abrasion-resistant.
 7.1  Standard Flat-Substrate Focusing Gratings标准平板基板聚焦光栅The focal length of all gratings is 3.75 mm. All gratings are designed to provide laser feedback via the first diffraction order. The working distance between grating and laser diode front facet is d = 7.5 mm for all gratings. Silicon substrate has a thickness of 0.73mm. Substrate height and width tolerances are 0.3 mm. Grating substrate: single crystal silicon. Grating coating: aluminum (other coating types are available at additional charge).

Part Number	Design Wavelength (nm)	Design Input Polarization1	Incidence Angle1 φ	Approx. Line Density2 (l/mm)	Size 1 (w × h)
SCG-405S-0603A-Al	405	s	40 °	3175	6 mm × 3 mm
SCG-405P-0306A-Al	405	p	45 °	3640	3 mm × 6 mm
SCG-635S-0603A-Al	635	s	40 °	2028	6 mm × 3 mm
SCG-635P-0306A-Al	635	p	65 °	2857	3 mm × 6 mm
SCG-780P-0306A-Al	780	p	60 °	2222	3 mm × 6 mm

8. Self-Calibrating Gratings自校准光栅LightSmyth has a new concept in grating design – gratings with integral calibration features. A user of these gratings will enjoy the same high performance and low cost of low scatter reflection gratings with the additional benefit of advanced wavelength calibration offered by a thin array of embedded micro-gratings. A schematic representation of such a grating is shown in the figure to the right. The Primary Grating is used in the traditional manner, but the 12 alignment/calibration gratings, when illuminated by a HeNe laser or other reference, provide a family of calibration markers in the detection plane. These markers allow high precision and convenient calibration of the Primary Gratings dispersion line. As described in the application note “Gratings with Integral Calibration Features“, the markers also allow precise monitoring of the input signal wavefront and the proper detection-plane focus. Significantly, the primary grating wavelengths indicated by the markers are independent of the angle of incidence of the input light. Essentially, one is calibrating the primary grating’s output plane through differential comparison of the ratio of line densities of the primary and alignment/calibration gratings.
In this product, the Primary and alignment/calibration gratings are spatially coherent (i.e. positioned with interferometric accuracy relative to one another) and are part of a single monolithic structure. The product comes in two versions. In the first, the lines of all gratings are parallel and marker output signals fall along the dispersion line of the Primary Grating. In the second, lines of the alignment/calibration gratings have tilts precisely calculated to provide NeHe generated markers that fall along a line slightly displaced from but parallel to the Primary Grating dispersion line. Alternative reference light sources can be employed as well in which case calibration markers are still precisely correlated with specific primary grating output wavelengths in an input-angle-independent manner. The markers shift their primary grating reference wavelength (as given in Table 1) in proportion to the ratio of the new reference wavelength divided by 632.8 nm.
Table 1 details the properties of both the tilted and non-tilted versions of the product. One inch gratings contain the full set of 12 alignment/calibration gratings. Half-inch gratings contain a subset of 6. The alignment/calibration gratings are designed so that subsets of 6 gratings provide a useful set of markers. For Table 1, signal light is incident at 30 degrees from the normal on the same side as the output. Other input angles may be employed without changing the marker wavelengths.

Table 1
Grating	First-order Marker wavelength* (nm)	Lines/mm (non-tilted)	Lines/mm (tilted)	Tilt angle (º)
Primary	N/A	1200	1200	0
1	400	758.6	760.6	4.158
2	500	948.2	949.8	3.329
3	600	1137.7	1139.1	2.775
4	700	1327.4	1328.6	2.379
5	800	1517.2	1518.2	2.082
6	900	1706.7	1707.6	1.851
7	500	948.2	949.8	3.329
8	550	1043.0	1044.4	3.025
9	600	1137.7	1139.1	2.775
10	650	1232.6	1233.9	2.560
11	700	1327.4	1328.6	2.379
12	750	1422.2	1423.3	2.219
* First-order marker wavelength is the wavelength of light diffracted from the primary grating which falls at the same output angle as the HeNe marker signal from the referenced alignment/calibration grating. Note that alignment/calibration gratings produce additional HeNe markers at higher orders and that the marker wavelength is simply multiplied by the order number.

8.1  List of Standard Gratings with Calibration FeaturesTypical grating thickness: approximately 0.73 mm
Substrate height and width tolerance: 0.3 mm
Grating substrate: single crystal silicon
Grating coating: aluminum (other coating types are optional)

Part Number	Primary Grating Line Density (Lines/mm)	Alignment/Calibration Gratings	Orientation	Size (mm)
CNG-C12-1212A-Al	1200	1-6 or 7-12	Non-tilt	12.5 × 12.5
CNG-C12-252-Al	1200	1-12	Non-tilt	25  × 25
CTG-C12-1212A-Al	1200	1-6 or 7-12	Tilt	12.5  × 12.5
CTG-C12-252-Al	1200	1-12	Tilt	25  × 25

9. Coherent Grating Arrays相干光栅组LightSmyth is proud to introduce monolithic, single-substrate, silicon grating arrays (Figure 1) that uniquely provide continuous high-resolution access to optical bandwidths beyond that achievable with a single grating. No moving parts are required. LightSmyth’s monolithic grating arrays are consistent with single-shot data acquisition for many broadband applications (e.g. laser-induced breakdown spectroscopy and can help reduce system component numbers dramatically). Each array consists of multiple primary gratings all formed coherently on a single substrate. The primary gratings have contiguous, slightly overlapping active spectral ranges. Additionally, auxiliary gratings at the top and bottom of the substrate produce optical outputs used for the straightforward calibration of the output field using a single reference wavelength such as a HeNe laser.
Calibration/Alignment Features 校准对齐功能
The six small gratings at the top and bottom of the array (reference Figure 1) provide markers for calibrating the spectral output as well as assisting in system alignment. The calibration marks, here for HeNe illumination, are shown schematically in Figure 4. The calibration marks provide two principal functions:

1. They indicate the beginning and end points of the calibrated portion of the primary grating output. They thus allow the user to calibrate the wavelength as a function of position along each of the primary gratings dispersion lines.  Note that the wavelength range denoted by the calibration spots is independent of the grating input angle, making the LightSmyth grating array extraordinarily versatile with respect to possible device layouts.
2. The auxiliary gratings aid in system alignment. When the detector surface is properly positioned in the focal plane of the post-array focusing mirror, the two pairs of alignment marks are designed to coincide, indicating proper far-field operation. The two center marks enable correct horizontal alignment of array and detector surface. 

Monolithic Silicon Grating Array单片硅阵列光栅
Silicon substrate has a thickness of 0.73mm. Substrate height and width tolerances are 0.3 mm. Grating substrate: single crystal silicon. Grating coating: aluminum (other coating types are available at additional charge).
More technical details regarding the monolithic grating array can be found in Application Note: Monolithic Silicon Grating Arrays.

Part Number	Primary Grating	Calibration Markers1	Line/mm	Size	Price first 99 units 2,3	Unit price 100+
SAG-1212A-Al	1	381, 522 nm	1788	12.5mm x 12.5mm	$96.00 ea.	$25.00 ea.
	2	509, 696 nm	1341
	3	683, 935 nm	998
	4	929, 1271 nm	734
1The calibration markers listed are produced by a HeNe laser incident on the small calibration gratings. Use of a different calibration light source having a different wavelength will produce markers (see Fig. 4) coinciding with different values of the dispersed spectra of the four primary gratings. Using a common input angle for calibration light and signal, the calibration marks delineate spectral output ranges of the primary gratings that are independent of grating input angle.
2 For orders with the total product value below $250.00, a handling charge of $75.00 will be added.
3 Academic discounts are available for eligible institutions. To determine eligibility complete an account application procedure.