多重全息图热固定的研究
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摘要
光折变晶体是在大容量全息存储中应用最为广泛的一种介质。根据电荷的激发和输
运机理，电荷场在晶体中形成电子光栅，以存储光信息。然而，这种机制也导致了光
照下全息图的光擦除。因此，在光折变晶体中记录的全息光栅不能长时间保存。为了
克服全息光栅读出过程的光擦除作用，提出了几种固定方法，包括电固定、热固定和
光固定技术。其中，热固定是研究最多的、最有效的固定方法。热固定的过程包括两
个步骤：固定和显影。在固定阶段，晶体中的离子在高温下运动，形成补偿电子光栅
的离子光栅。在显影阶段，电子光栅被擦除，显现出离子光栅。
应用分批方法，将需要存储在晶体同一位置的所有全息图分为若干批次，每组在室
温下记录，然后高温定影，当所有组次都记录、固定完成后，统一显影。因此，分批
热固定包括下列过程：电子光栅被同一组中后续记录的光栅的光擦除和不同组次记录
光栅时的光擦除；离子光栅在热固定时对同组内电子光栅的补偿和后续组次固定时对
前组离子光栅的平滑作用。根据光擦除和离子光栅在后续组次热固定过程中的多次平
滑作用，设计了测量组间擦除时间常数的分批热固定实验。根据在所有组次中的每组
衍射效率，选择了双掺LiNbO_3晶体。实验结果表明：组间擦除时间常数远大于常规擦
除时间常数。其原因是光致电子的运动被相应的离子光栅阻碍，离子光栅对电子光栅
的屏蔽效应减慢了不同组次间的光擦除。通过对单次和分批热固定的实验测量了固定
次数对图像质量的影响。结果证明多次热固定过程对图像质量的影响并不明显。最后，
通过测量重构全息图的信噪比，拟和出暗保存时间。
Photorefractive crystals are commonly used as a recording medium in volume
holographic storage. According to the charge excitation and transport mechanism, the
electronic charges constitute holograms in photorefractive crystals to store some desired
optical information. However, the above mentioned mechanism similarly causes optical
erasure of holograms in further illumination process. Therefore, the recorded holographic
gratings are not permanently maintained in photorefractive crystals. In order to overcome
such optical erasure to holograms on readout, several fixing methods developed, including
electric fixing.. thermal fixing and optical nonvolatile readout techniques. Among them,
thermal fixing is the most active and effective technique. The procedure of thermal fixing
includes two steps: fixing and developing. In fixing stage, the ions in crystals move to form
an ionic grating and neutralize the electronic grating at elevated temperature. In developing
stage, a homogeneous illumination erases the electronic grating and brings out the ionic
grating when cooling to room temperature.
Using the batch method, all the holograms to be stored in one location of a crystal are
divided into several batches, each batch is recorded at room temperature and followed by a
fixing process at higher temperature fixed at higher temperature. After all batches are
recorded and fixed, they are revealed in whole at room temperature. Therefore, the batch
procedure of thermal fixing includes the following processes: optical erasure of electronic
gratings both by subsequent recordings in the same batch and by recordings in subsequent
batches; ionic compensation during thermal fixing in one batch; smoothing of ionic gratings
during thermal fixing of subsequent batches; and revealing of fixed ionic gratings. Based on
mechanism of both optical erasure and smoothing repeated in batch scheme, an experiment
of thermal fixing for multiplexed holograms to measure the optical erasure time constant of
inter-batch for given crystal samples was further designed. Inter-batch optical erasure time
constant was fitted out for co-doped lithium niobate crystals according to the diffraction
efficiency measured in every stage of all the batches. Experimental results indicate that inter-
batch optical erasure time constant t~ is indeed much longer than ordinary erasure time
constant tE. The reason is that the migration of light-induced electrons are hampered by
Abstract
corresponding ionic gratings, screening effect of ionic gratings on electronic ones, can slow
optical erasure in different batches. The effect of the fixing number on the quality of
holograms was measured through the experiments on both single-scheme and batch-scheme
of thermal fixing. The results show that the repeated fixing processes have not observable
effect on the quality of holograms. Finally, the dark storage time was fitted out via
measuring signal-noise ratio of the reconstructed hologram.
运机理，电荷场在晶体中形成电子光栅，以存储光信息。然而，这种机制也导致了光
照下全息图的光擦除。因此，在光折变晶体中记录的全息光栅不能长时间保存。为了
克服全息光栅读出过程的光擦除作用，提出了几种固定方法，包括电固定、热固定和
光固定技术。其中，热固定是研究最多的、最有效的固定方法。热固定的过程包括两
个步骤：固定和显影。在固定阶段，晶体中的离子在高温下运动，形成补偿电子光栅
的离子光栅。在显影阶段，电子光栅被擦除，显现出离子光栅。
应用分批方法，将需要存储在晶体同一位置的所有全息图分为若干批次，每组在室
温下记录，然后高温定影，当所有组次都记录、固定完成后，统一显影。因此，分批
热固定包括下列过程：电子光栅被同一组中后续记录的光栅的光擦除和不同组次记录
光栅时的光擦除；离子光栅在热固定时对同组内电子光栅的补偿和后续组次固定时对
前组离子光栅的平滑作用。根据光擦除和离子光栅在后续组次热固定过程中的多次平
滑作用，设计了测量组间擦除时间常数的分批热固定实验。根据在所有组次中的每组
衍射效率，选择了双掺LiNbO_3晶体。实验结果表明：组间擦除时间常数远大于常规擦
除时间常数。其原因是光致电子的运动被相应的离子光栅阻碍，离子光栅对电子光栅
的屏蔽效应减慢了不同组次间的光擦除。通过对单次和分批热固定的实验测量了固定
次数对图像质量的影响。结果证明多次热固定过程对图像质量的影响并不明显。最后，
通过测量重构全息图的信噪比，拟和出暗保存时间。
Photorefractive crystals are commonly used as a recording medium in volume
holographic storage. According to the charge excitation and transport mechanism, the
electronic charges constitute holograms in photorefractive crystals to store some desired
optical information. However, the above mentioned mechanism similarly causes optical
erasure of holograms in further illumination process. Therefore, the recorded holographic
gratings are not permanently maintained in photorefractive crystals. In order to overcome
such optical erasure to holograms on readout, several fixing methods developed, including
electric fixing.. thermal fixing and optical nonvolatile readout techniques. Among them,
thermal fixing is the most active and effective technique. The procedure of thermal fixing
includes two steps: fixing and developing. In fixing stage, the ions in crystals move to form
an ionic grating and neutralize the electronic grating at elevated temperature. In developing
stage, a homogeneous illumination erases the electronic grating and brings out the ionic
grating when cooling to room temperature.
Using the batch method, all the holograms to be stored in one location of a crystal are
divided into several batches, each batch is recorded at room temperature and followed by a
fixing process at higher temperature fixed at higher temperature. After all batches are
recorded and fixed, they are revealed in whole at room temperature. Therefore, the batch
procedure of thermal fixing includes the following processes: optical erasure of electronic
gratings both by subsequent recordings in the same batch and by recordings in subsequent
batches; ionic compensation during thermal fixing in one batch; smoothing of ionic gratings
during thermal fixing of subsequent batches; and revealing of fixed ionic gratings. Based on
mechanism of both optical erasure and smoothing repeated in batch scheme, an experiment
of thermal fixing for multiplexed holograms to measure the optical erasure time constant of
inter-batch for given crystal samples was further designed. Inter-batch optical erasure time
constant was fitted out for co-doped lithium niobate crystals according to the diffraction
efficiency measured in every stage of all the batches. Experimental results indicate that inter-
batch optical erasure time constant t~ is indeed much longer than ordinary erasure time
constant tE. The reason is that the migration of light-induced electrons are hampered by
Abstract
corresponding ionic gratings, screening effect of ionic gratings on electronic ones, can slow
optical erasure in different batches. The effect of the fixing number on the quality of
holograms was measured through the experiments on both single-scheme and batch-scheme
of thermal fixing. The results show that the repeated fixing processes have not observable
effect on the quality of holograms. Finally, the dark storage time was fitted out via
measuring signal-noise ratio of the reconstructed hologram.
引文
[1] Yong Qiao，Sergei Orlov，Demetri Psaltis，and R．R．Neurgaonkar，“Electrical fixing of photorefractive holograms in Sr0． 75 Ba0． 25 Nb2O6”，Opt．Lett．(1993) ，18(12) ，1004-1006．
[2] V．Leyva，A．Agranat，and B．Fischer，Opt．Lett．(1991) ，22，1964．
[3] Jian Ma，Tallis Chang，John Hong，R．Neurgaonkar，G．Barbastathis，and Demetri psaltis，“Electrical fixing of 1000 angle-multiplexed holograms in SBN：75”，Opt．Lett．(1997) ，22(14) ，1116-1118．
[4] A．Adibi，K．Buse，and D．Psaltis，“Multiplexing holograms in LiNbO3：Fe：Mn crystals，”Opt．Lett．， 24(10) ，652-654(1999) ．]
[5] J．J．Amodei and D．L．Staebler，“Holographic pattern fixing in electro-optic crystals”，Appl．Phys． Lett．(1971) ，18，540-542．
[6] H．Vormann，G．Weber，S．Kapphan，and E．Kratzig，“Hydrogen as origin of thermal fixing in LiNbO3：Fe”，Solid State Communications，(1981) ，40，543-545．
[7] P．Hertel，K．H．Ringhofer，and R．Sommerfeldt,“Theory of thermal hologram fixing and application to LiNbO3：Cu”，Phys．Status Solidi A，(1987) ，104，855-862．
[8] M．Carrascosa and F．Agullo-Lopez，“Theoretical modeling of the fixing and developing of holographic gratings in LiNbO3”，J.Opt．Soc．Am．．B，(1990) ，7(12) ，2317-2322．
[9] Ammon Yariv，Sergei S．Orlov，and George A．Rakuljic，“Holographic storage dynamics in lithium niobate：theory and experiment”,J.Opt．Soe．Am．B,(1996) ，13(11) ，2513-2523．
[10] L．Arizmendi，P．D．Townnsendt，M．Carrascosa，J．Baquedano．and J．M．Cabrera，“Photorefractive fixing and related thermal effects in LiNbO3”，J. Phys．: Condens．Matter,(1991) ，3，5399-5406．
[11] S．Breer，k．Buse，and F．Rickermann，“Improved development of thermally fixed holograms in photorefractive LiNbO3”，Opt．lett．(1998) ，23(1) ，73-75．
[12] M．Carrascosa and F．Agullo-lopez，“Optimization of the developing stage for fixed gratings in LiNbO3”，Opt．Commun．(1996) ，126，240-246．
[13] George A．Rakuljic，“Prescription for long-lifetime，high-diffraction-efficiency fixed holograms in Fe-doped LiNbO3”，Opt．Lett．(1997) ，22(11) ，825-827．
[14] L．Arizmendi，A．Mendez，and J．V．Alvarez-Bravo，“Stability of fixed holograms in LiNbO3”，Appl． Phys．Lett．(1997) ，70(5) ，571-573．
[15] D．L．Staebler，W．J．Burke，W．Phillips，and Amodei，“Multiple storage and erasure of fixed holograms in Fe-doped LiNbO3”，Appl．Phys．Lett．(1975) ，26(4) ，182-184．
[16] J．F．Heanue，M．C．Bashaw,A．J．Daiber，R．Snyder，and L．Hesselink，“Digital holographic storage system incorporating thermal fixing in lithium niobate”,Opt．Lett．(1996) ，21(19) ，1615-1617．
[17] Xin An,D．Psaltis，and Geoffrey W．Burr，“Thermal fixing of 10000 holograms in LiNbO3：Fe，” Appl．Opt．，38(2) ，386-393(1999)
[18] 宋雪华“光折变晶体中全息图的热固定”北京工业大学硕士论文(1999． 5)
[19] 陶世荃、王大勇、江竹青、袁泉“光全息存储”北京工业大学出版社(1998)
[20] 江竹青，孟纲，陶世荃“光折变晶体中多重全息图分批定影热固定的研究”(激光杂志)
[2l] 唐斌，陶世荃，江竹青，王大勇,沈兰荪，“光折变晶体全息存储的灰度保真度”博士论文
[22] J．F．Heanue，K．Gurkan and L．Hesselink，“Signal detection for page-access optical memories with intersymbol interference”， Appl．Opt．， vol．35， no．14， P．2431～2438(1996) ．
[23] Claire Gu，Gregory Sornat and John Hong，“Bit-error rate and statistics of complex amplitude noise in holographic data storage”， Opt．Lett．， vol．21， no．14， P．1070～1072(1996) ．
[24] F．H．Mok，D．Psaltis and G．Burr，“Spatially-and Angle-multiplexed holographic random access memory”，SPIE,vol．1773，P．334～345(1992) ．
[25] Xin An and D．Psaltis，“Experimental characterization of an angle-multiplexed holographic memory”，Opt．Lett．，vol．20，no．18，P．1913～1915(1995) ．
[26] M．A．Neifeld and M．McDonald，“Technique for controlling cross-talk noise in volume holography”，Opt．Lett．，vol．21，no．16，P．1298～1300(1996) ．
[27] Allen Pu and Demetri Psaltis，“High-density recording in photopolymer-based holographic three-dimensional disks”，Appl．Opt．，vol．35，no．14． ，P．2389～2398(1996) ．
[28] Gregory P．Nordin and Praveen Asthana，“Effects of cross talk on fidelity in page-oriented volume holographic optical data storage”，opt．Lett．，vol．18，no．18， P．1553～1555(1993) ．
[2] V．Leyva，A．Agranat，and B．Fischer，Opt．Lett．(1991) ，22，1964．
[3] Jian Ma，Tallis Chang，John Hong，R．Neurgaonkar，G．Barbastathis，and Demetri psaltis，“Electrical fixing of 1000 angle-multiplexed holograms in SBN：75”，Opt．Lett．(1997) ，22(14) ，1116-1118．
[4] A．Adibi，K．Buse，and D．Psaltis，“Multiplexing holograms in LiNbO3：Fe：Mn crystals，”Opt．Lett．， 24(10) ，652-654(1999) ．]
[5] J．J．Amodei and D．L．Staebler，“Holographic pattern fixing in electro-optic crystals”，Appl．Phys． Lett．(1971) ，18，540-542．
[6] H．Vormann，G．Weber，S．Kapphan，and E．Kratzig，“Hydrogen as origin of thermal fixing in LiNbO3：Fe”，Solid State Communications，(1981) ，40，543-545．
[7] P．Hertel，K．H．Ringhofer，and R．Sommerfeldt,“Theory of thermal hologram fixing and application to LiNbO3：Cu”，Phys．Status Solidi A，(1987) ，104，855-862．
[8] M．Carrascosa and F．Agullo-Lopez，“Theoretical modeling of the fixing and developing of holographic gratings in LiNbO3”，J.Opt．Soc．Am．．B，(1990) ，7(12) ，2317-2322．
[9] Ammon Yariv，Sergei S．Orlov，and George A．Rakuljic，“Holographic storage dynamics in lithium niobate：theory and experiment”,J.Opt．Soe．Am．B,(1996) ，13(11) ，2513-2523．
[10] L．Arizmendi，P．D．Townnsendt，M．Carrascosa，J．Baquedano．and J．M．Cabrera，“Photorefractive fixing and related thermal effects in LiNbO3”，J. Phys．: Condens．Matter,(1991) ，3，5399-5406．
[11] S．Breer，k．Buse，and F．Rickermann，“Improved development of thermally fixed holograms in photorefractive LiNbO3”，Opt．lett．(1998) ，23(1) ，73-75．
[12] M．Carrascosa and F．Agullo-lopez，“Optimization of the developing stage for fixed gratings in LiNbO3”，Opt．Commun．(1996) ，126，240-246．
[13] George A．Rakuljic，“Prescription for long-lifetime，high-diffraction-efficiency fixed holograms in Fe-doped LiNbO3”，Opt．Lett．(1997) ，22(11) ，825-827．
[14] L．Arizmendi，A．Mendez，and J．V．Alvarez-Bravo，“Stability of fixed holograms in LiNbO3”，Appl． Phys．Lett．(1997) ，70(5) ，571-573．
[15] D．L．Staebler，W．J．Burke，W．Phillips，and Amodei，“Multiple storage and erasure of fixed holograms in Fe-doped LiNbO3”，Appl．Phys．Lett．(1975) ，26(4) ，182-184．
[16] J．F．Heanue，M．C．Bashaw,A．J．Daiber，R．Snyder，and L．Hesselink，“Digital holographic storage system incorporating thermal fixing in lithium niobate”,Opt．Lett．(1996) ，21(19) ，1615-1617．
[17] Xin An,D．Psaltis，and Geoffrey W．Burr，“Thermal fixing of 10000 holograms in LiNbO3：Fe，” Appl．Opt．，38(2) ，386-393(1999)
[18] 宋雪华“光折变晶体中全息图的热固定”北京工业大学硕士论文(1999． 5)
[19] 陶世荃、王大勇、江竹青、袁泉“光全息存储”北京工业大学出版社(1998)
[20] 江竹青，孟纲，陶世荃“光折变晶体中多重全息图分批定影热固定的研究”(激光杂志)
[2l] 唐斌，陶世荃，江竹青，王大勇,沈兰荪，“光折变晶体全息存储的灰度保真度”博士论文
[22] J．F．Heanue，K．Gurkan and L．Hesselink，“Signal detection for page-access optical memories with intersymbol interference”， Appl．Opt．， vol．35， no．14， P．2431～2438(1996) ．
[23] Claire Gu，Gregory Sornat and John Hong，“Bit-error rate and statistics of complex amplitude noise in holographic data storage”， Opt．Lett．， vol．21， no．14， P．1070～1072(1996) ．
[24] F．H．Mok，D．Psaltis and G．Burr，“Spatially-and Angle-multiplexed holographic random access memory”，SPIE,vol．1773，P．334～345(1992) ．
[25] Xin An and D．Psaltis，“Experimental characterization of an angle-multiplexed holographic memory”，Opt．Lett．，vol．20，no．18，P．1913～1915(1995) ．
[26] M．A．Neifeld and M．McDonald，“Technique for controlling cross-talk noise in volume holography”，Opt．Lett．，vol．21，no．16，P．1298～1300(1996) ．
[27] Allen Pu and Demetri Psaltis，“High-density recording in photopolymer-based holographic three-dimensional disks”，Appl．Opt．，vol．35，no．14． ，P．2389～2398(1996) ．
[28] Gregory P．Nordin and Praveen Asthana，“Effects of cross talk on fidelity in page-oriented volume holographic optical data storage”，opt．Lett．，vol．18，no．18， P．1553～1555(1993) ．